The limited surviving evidence, like this painted wooden board from a temple, suggests that ancient Greeks did wear brightly colored clothing. This makes sense, since producing from raw fibers cloth was very labor-intensive in pre-modern times, but dying the cloth is fairly straightforward and takes relatively little time and effort, compared to that needed to make the cloth.

This article may also be relevant to your interests: http://www.smithsonianmag.com/arts-culture/bringing-the-color-back-to-ancient-greece-80032254/