first of all
you did a great restauration job on this pic
all i can really think of is that you could convert your layer to greyscale and make new layers, put them to color and paint in the colors by hand
there are great tutorials in this site where you can read the basics for that job
I've read it and it's really not that hard :p
good luck
mdivad
ps: Im playing around with your pic but i cant make a great job now cause my boss is watching so i dont surf the web.... lucky me he's not that smart hahaha