in addition to what Mark has shared above, you can export your artrage files as .png or .psd documents and edit them in a 3-rd party application you have more experience with that has advanced color grading instruments.
you can split paint and paint depth channels and export them separately, if you need that much fidelity, as well.
I barely edit my artrage paintings color-wise because I tend to pre-mix the exact color harmonies I have in my mind as I paint, and this is the major part of the artrage experience - it mixes paint in a fantastic, impeccable way - but if you need complex color correction, that part is better taken to a specialized app.