>>1973791Depends on the best effect - Usually, it's easiest to do a color picker and grab the colors. But there are times when you'll want to grab and use a dark blue or red too add warmth to the shadow. Don't use black or white if possible unless it really suits the affect you're going for - effects themselves can be changes as needed.
Using the image pasted as an example: I used blues and reds to make the shadows in this to give them a better fit to the image - I had to do the image's color fro scratch, as the image was washed out. The hair actually has black as a shadow color.
Hope this gives some help to you...