What color to paint an ugly brick fireplace?  

Tell
that to an artist. . .! It's a good rule to follow, in the absence of some divine inspiration to the contrary. The world needs both: the modest and accommodating background, and the colorful and assertive foreground.
There are many instances of brick building intended to be painted from the start; the color is typically white. The poster who pointed out that not all brick is handsome enough to be seen naked, had a point -- though there are those of us who think all well-laid masonry looks good in its natural state -- as "god" intended ?

.
That was me who said NOT all natural brick is great...Also its amazing how most people here feel/think:Neutral is best.SDR there is a large hispanic population here in Austin Tx. who seem to favor the cardboard xmas display paint job:bright red bricks ,joints picked out in snow white...really not a suble or good look...A classic treatment is white/off white painted brick...boring?

.
what about a soot coloured black? Or a dark slate blue grey?

natural is best but if ...
natural is best but if you are gonna paint go light as that will blend with every thing
If you ever have any kind of natural stone and even think of painting it i will personally fly over and kick your butt that is a sin to paint natural stone inside or out,
with one exception, here in Oklahoma some contractors found cheap stone quary , that had brown sand stone and started using it in the 1970s on contemporary homes, as they do not deserve to be called modern, and they are the most ugly homes in America, they used ugly grey and brown motor and big hugs of the brown stand stone really ugly, and the doors were so cheap and every one had to put a glass security store to open the heavy door to let the light in,
any other color of light sand stone can be very nice looking as made popular by the Harvard five in all the homes in the late 40s and 50's . Elliott Noyes, John Johnason, Landis Gores, Phillip Johnson, and Marcel Breur all loved the natural stone and interagrted in there homes as Well as Frank Lloyd Wright , a new contest we should sponsor. the Ugly house contest,

I like
those dark suggestions, though a flat black (which I've seen) didn't attract me. Too much like a disused basement somewhere ? The dark slate blue-gray sounds good. I don't necessarily agree that a light tone is the only way to go.
Yes, pale color is a good standby. A brick wall painted the same color as the room can look very neat and tailored, or it can look like something found in a much-painted but unloved old firetrap. It would have to do with other details in the space, I suppose. I was just arguing for making use of the existing color for the reasons stated, and trying for something that would stand on its own, suggest real masonry, and relate in some way to the other color choices present. It sounded like that's what the tenant was after.
I would always argue for returning masonry to its virgin state if that was possible. If the whole place was empty and undergoing renovation, I guess I'd think about to stripping or abrading the paint off. A big and nasty job, but you could always quit if it looked like a losing proposition.
The chemical method used in the link was an outdoor job, and required lots of rinsing (flooding ?) as I recall. But it worked, on rough stone.

I guess
LRF must have found this. Nice house, Mr Gores !
http://www.lottaliving.com/bb/viewtopic.php?t=10822&start=60

As to
ugly houses, LL beat us to it. (At least we have a better-looking board !)
Hint: Start at the end, if you're pressed for time. Moderns-R-Us is a Kansan City architect and mid-century modern aficianado, and a friend. Good guy. Enjoy.
http://www.lottaliving.com/bb/viewtopic.php?t=3647&sid=cdf92d294b3cd8482...

Thanks for all your suggestions!!
I went and bought a bunch of the Benjamin Moore Color samples.The best to my eye,and as you suggested was a clay color-"Pumpkin Patch",I think color #55 in an Eggshell finish.I spent the better part of the day painting every nook and cranny,just smashing the unthinned paint into the crevices,to make sure I had ample coverage.At first I was horrified,as it seemed too bright.Now we all know paint darkens as it dries,so I took a look in the morning light,and Wow! I must say I am most pleased!The newly painted brick has some verve instead of just being an ugly amorphous mass.Looks great with all the elements in the room too! The dark brown grout thing wasn't gonna work ,but thanks for your thoughtfulness and all your suggestions!Thanks fellow DA'ers! If I ever take pics,I will certainly post them!

Several of the brick homes...
in the neighborhood I grew up in are painted. Why? Because whoever was the yahoo who built some of the homes used green, white, and yellow bricks. I think maybe there were about five houses that used that color scheme for the bricks. They are THE tackiest looking bricks you'll ever see. My step-father has refused to paint the house so it is the only remaining green, white, and yellow brick house in the neighborhood. It is a very nice house other than the butt-ugly bricks. My mother also hates the brick colors. The green, white, and yellow bricks were also carried over into the inside of the house...on the walls with the fireplaces and on the bar that separates the living room and kitchen. It was hideous. When my step-dad was on a business trip once, we painted over all the bricks inside to match the other colors in the living room and kitchen...a light robins egg blue. It actually turned out nicely. Much better than the green, white, and yellow. My step-dad almost blew a fuse when he got home. He actually likes the green, white, and yellow. But mom said she vetoed him. He could keep the ugly bricks on the outside, but she was controlling the color scheme inside. My step-dad has absolutely no taste. He'd by the cheapest of everything no matter how tacky-looking just to save a few dollars. Luckily, my mom has better taste then him 🙂
I think my parents are finally getting ready to down-size since my little brother has finally moved out. I informed them that if they want to get a decent price they would have to paint because the first impression of the house, the outside of it, is such a turn-off. And first impressions are everything when selling a home. So my word of advice, DO NOT under any circumstances paint your bricks green, white, and yellow.

.
That brick sounds like (indian corn)but I do like the mixed in the corn...I agree with you, your parents will get more if its painted in keeping with all the others in the neighborhood.Pastels/brights can look cheap esp outside.Also about the pale blue inside...pale blue is often one of the cheapest looking colors, Ive read...but then we have the classic Tiffany box...

Well, the pale blue...
on the fireplace and bar bricks looks okay. Definitely better than the mix of green, white, and yellow bricks. My mom chose the colors. She chose that shade because it complimented her decor. Actually, it might not be that color anymore. I know they have recently had the inside of the house professionally re-painted since they are getting it ready to sale in the next year or so. Don't know what colors they painted everything. I think their next project is replacing the carpets. And then maybe they'll paint the tacky bricks on the outside.
And I never got the feeling looking at the house that it looked like Indian corn. It just looked like it was some 70s fad that was only popular for like two minutes before everyone decided it was tacky.

Toilet tone
Get the glossiest brilliant white enamel you can find and slap it on......yep, it might make you want to pee from time to time but I rekon it's the best way to go !

I was thinking white, myself...
But GLOSSY? On brick? Are you SURE you want every little nook & cranny highlighted, like that?

Certainly not.
.

Here's another option.
If you love the fireplace and want it to stay brick, then get a professional sander and sand it smooth and cement new brick facing over it.