Hair coloring steps:

# go to quick-mask-mode by pressing Q

# using SOFT EDGE brush paint the hair

# now press q again. Whatever you have NOT painted becomes selected

# inverse the selection,now hair only is selected

# create a new layer and fill the selected area with say red color

# select SOFTLIGHT instead of NORMAL from drop down in the layers window

#what techniques we learnt:

QUICK MASK MODE : it  is nothing but selection by painting.

SOFTLIGHT: It is one of  the diffusion manners. Other manners are hardlight,dissolve,multiply,etc.