Yes it's true. The color makes a difference with the feel of the overgrip, at least it does for me. I used the black yonex supergrap for a while, and realized that it was causing painful blisters. I switched to the white color supergrap, and it felt MUCH softer, resulting in zero blisters.
I switched to the wilson overgrip because it pretty much felt the same compared to the white yonex, and came in packs of 30.