Hi Sara and welcome to the PSG forum. I hope you will come to appreciate it as much as I do
I am sorry to hear that you've lost your grandparents. I have made a very quick attempt at colouring your photo (a 5-minute work) so take it for what it is - an example.
I copied the image and paste it as a new layer in PS. And colorized the complete layer ([CTRL+U]). Using the eraser I removed everything except the skin. This procedure was repted for the "hat", the Sari (?) etc. If you want the PSD to tweak the colors just let me know.
There is also a lot of tutorials on colouring photos, just Google for it.
Is this a scanned version of your only photo? If so you should try to scan it once again 'cause the quality of the image isn't too good. It's a lot of "pixels" in it. Look at the "hat" and you'll see what I mean.
BTW they are very beatiful and have a "proud" look.
/Moltas