Garden wall color: white, black or gray?

My organic garden abuts the back of my garage which is cinderblock and absorbs and then radiates heat throughout the day. I plant my tomatoes there for that reason.
It is currently a light gray color and I'm thinking of painting it a more reflective white, because the garden  is partially shaded until about 11AM and so I thought this might help all the plants.
I'm also considering black to absorb more heat, but as it is, it seems to do a pretty good job of radiating the days stored heat now.
Anyone have experience with painting a wall white and if it makes a difference to the plants?

I've been told that white makes a difference, by someone who's Dad did a lot of growing. However, that doesn't mean the suggestion was accurate, as I suspect they were following popular advice which may not have "before and after" back-up. However, my friend specifically said that the value of the white reflecting light was greater than the value of having the wall black for heat absorption.

That said, if you also want to improve the heat retention, and you don't need the heat in the garage, insulating the garage side of the blocks might be worthwhile to consider.

What I have experienced myself is that the glare off white surfaces is hard on my eyes, so I would consider whether you or others would experience that, as it might impact the final decision. The plants will only be covering the wall for part of the year?

If you're going to always(out at least frequently) grow your tomatoes there, you might actually want to consider painting it red. Tomatoes, according to some studies, apparently do substantially better, with red surroundings. I don't understand why, but I have to admit, last year my tomatoes did much better than they have in the last several years - and for the first time, I'd planted them in giant red tubs...

If you're set on black or white, consider the summer heat, where you are. Over heated tomatoes don't do well, for me, and need more frequent watering, to survive. If yours need more heat in the summer, I'd go with the black. But, here, mine would wither and die, before noon, the first hot day.