I can't color some parts of my model I am sorry if someone already asked for this question, I wasn't able to find it anywhere..I googled lots of things and didn't satisfied my needs so I hope you can help me out :) :P.
When I try to hand texture my model, some parts are being unable to be textured.
I hope you understand what I mean, here is a screenshot so I can explain you.


The blue line is showing where I can't texture it as you can see it's white.
I had to "Fill" to get the white color even though some places got still black as on the picture you can see black texture on the fore-end/near barrel.
Sometimes it's hard to paint some areas in the 3D Window. You may try going to UV Editor, change the mode from View to Paint and paint these areas there.