changing one colour to another?

i’m in post process, in my scene, i had white, but now i want my white to be slight magenta-ish colored, i thought, colour key! but i just kinda don’t know how to do it…
and not just this, sometimes, i need my blues to be orange at the end and the blues stay as blues, so i can’t really change the material colors(especially when i’m using cycles, there are colour bounces)
so, is there a way to turn a shade a white into a shade of magenta?

In the compositor you can add a Color correction node or Curves node. Just alter the white peak so that it is the only portion of the image altered.