One of the quickest way to come up with the right colors is to use ColorPicker. Simple, but with all the necessary features, it has hex input, a color slider and the ability to save colors to a palette. You can also choose from generated palettes with complementary, triade, tetrade

Useful for all kinds of color tasks that may otherwise require several programs, Colorzilla puts a lot of tools useful for web designers into a simple to use extension for Firefox. Get color readings that you can then adjust and paste into other programs, measure distance between two points on