I run a few websites now which means I have had a need to change colours on themes. However, being colourblind, this can be somewhat difficult to mke sure that the colours I am choosing will work together. One site I have found very useful is ColorHexa.com; this is a free color tool providing information about any color and generating matching color palettes for your designs (such as complementary, analogous, triadic, tetradic or monochromatic colors schemes).
The below screenshot shows part of the color palette generated for this sites main colour azure blue (#007FFF):
