Algorithm for calculating inverse color

Question

I have a RGB color in the range of 0.0 to 1.0 for each fragment, I need an algorithm to get the inverse of the color, any ideas how can I do this?

Answer 1

newR = 1.0 - r
newG = 1.0 - g
newB = 1.0 - b

If the color has a premultiplied Alpha value use the alpha instead of 1.0:

newR = a - r
newG = a - g
newB = a - b