MATCAP how and when to use this ?

can someone point to a good tut or intro to matcap in blender

i got the blend file from
http://bensimonds.com/2010/07/30/matcap-generator/

but then i cannot change the color in this file for the mat ?

andi guess you have to save this render as a PNG image or JPG
then reload it on a shadelss object GLSL mode and texture mode to see it
in another file

but when is it appropriate to use this

is it only for sculpt mode

Thanks happy 2.5

You can change color by messing with RGB Curves Node. Can’t you? As for render, it seems to work well with sculpt mode. But it is not limited to that. It’s just material with given looks.