What you are looking for is a way to select colors perceived as "light" by the human eye/brain. To do this you need to work in the HSL color space.
HSL is a way of expressing colors as H
ue, S
aturation and L
ightness, instead of Red, Green and Blue. What you'll need to do is research the algorithm for converting from HSL to RGB (there are lots of resources available on the web, including online converters).
You can cycle through all possible combinations of Hue and Saturation, limiting yourself to colors with lightness above some threshold. Then run those combinations through the conversion algorithm to get the RGB equivalents.