Thoughts on reupholstering these?  

RAL 1021
Or similar colors?! Good contrast and tone-sur-tone.... perhaps even more bright

Interesting. I hadn't even...
Interesting. I hadn't even considered a yellow. Neat.
For some more context, these would likely be used around a teak dining table.

oatmeal?
I concur on the yellows!

agree on bright....
and lets see an image of those pepper mills in the background!

Thanks all. I'll post up a...
Thanks all. I'll post up a photo of the pepper mill collection in the morning.

I'd go for a bright
olive green.
Maharam/Kvadrat Hallingdal 180:

I'd go black
knoll textiles: hourglass / caviar.

If the chairs are to set the scheme,
and, since opinions are like belly buttons, I have to agree with *spanky*. I've always thought that complementary colors work well with pieces that are almost equal parts upholstered and exposed wood. With teak, that means green.

Cool. I like that way of...
Cool. I like that way of thinking about it tktoo and *spanky*. It would seem to offer the best balance between teak and fabric.

Per request
Here's a closer up image of the pepper mills. Most are Dansk with a few odd balls. Some are in great condition, some only sculptural (mechanics not working), and some could just use some oil. The item on the far left is a nut cracker... but I really like it's geometric design.
Even larger image here:

Reupholstery
Check out page 30 of the new summer issue of Atomic Ranch magazine to see your chair done in black vinyl. Looks great!

Thanks for the heads up Hazelnut
Very cool! I don't have a subscription. Does it say anything about them? I haven't been able to find much information on them yet but do feel they're worthy of reupholstery.
Nest step: Time to some fabric samples.

Upholstery
It notes 'possibly by Kai Kristiansen'. Me thinks you're going to love them once you re-do.......

Z chair
They also referred to it as a 'Z' chair.....
Karin