Transparent color .dtx files...

Hi I'm currently trying to make transparent color in .dtx files, I have heard that some color in some dtx file aren't visible like "black" color... I tried with the M9 knife and it's not working well.

Does someone can help me ? I want to make some part of the M9 knife, transparent.

You can try to eliminate the texture using photoshop even if I do not know if after saving remains transparent.