At the moment it is only possible to extract a channel. For example:
blue := ImageEnView1.Proc.GetRGBChannel(0);
green := ImageEnView1.Proc.GetRGBChannel(1);
red := ImageEnView1.Proc.GetRGBChannel(2);
blue, green and red are gray scale TIEBitmap objects.
Waiting for a future SetRGBChannel method you can re-insert an extracted channel with a simple loop.