Pick colors from the photos...colors you know the person likes. I suggest you do a test print first....to check colors as they come from your printer. So you don't waste a good photo sheet ( at 3 for $10.00...kinda pricey)..I would take a piece of freezer paper, iron onto some cotton fabric (white or eggshell, depending on the look you want)...same fabric you will use in quilt...or as close as you can get, then print on the printer you will use.
Some (most of those I've done) come out pretty dark. Don't use the best printer setting..use better... my printers have Draft, Better, Best...use the middle one. When it's printed, let it air dry for a half an hour or so...then press, using a pressing sheet over it. Let it cool...pull off the freezer paper...If the colors are too dark...brighten the photo before printing.
Professional photos are great, but in my experience, they print darker...I usually use my photo software to clarify & brighten them a little.
Marge.
Oh, and I forgot to tell you in the email..on any picture larger than 4" square...I quilt on the photo...I use clear thread and trace the outline of the people, trees, etc. I just don't go over any faces, skin, etc.