How to make black show on a kit
1. Open your texture and set it to
multiply.
2. Set your base colour to
#1E1E1E or
RGB 30,30,30.
3. Make a new layer, then use the paint bucket to fill it with the black foreground colour and drag that layer beneath the texture layer.

4. Duplicate the texture layer
5. Set the blending mode to
Screen
6. Click on the bottom most texture layer and go to
Image>Adjust>Brightness/Contrast
7. Set Brightness to -100 and click OK, go back to the
Brightness/Contrast tab and now turn the brightness down to an amount which looks correct to you. (I had to turn mine down by -220)
Their you go your black colour should look something like this: