accessibility ( color change)

Hi
i’m currently a hnc student and as part of the course we’r building websites for clients( mine being the bvac) we are required to implement full accessibility features and this is were my problem lies,
alt tags are easy enough and i’ve found a few good plugins for text resizing but can’t seam to find one for color changing of the text and or background.
if anyone can point me in the direction of either a plugin/ widget that dose this or some code i can use to do it myself i’d be very grateful

– John