Yes some of this looks alot like another post, but its not copied...
Create a new 6x6...
Use the magnification tool untill your at max...
Make sure the forground color is black
Click on the pencil tool...
Make an X every other tile...(Make sure brush size is 1)
It should look like this:
Or pretty close...
Now click on the retangle marque tool thing, go to edit>define pattern
Use: Pattern
Opacity (i suggest 20-60%)
Mode: Normal
(Note: If it does not show these settings you have a different version of photoshop)
Now go to your image, Edit> fill, Select your pattern in the square box thingy Opacity 20-60% Then on the layer you put it in(Should be new) Select the opicity to like 30-60% and your done!
Mine looked like this(Of coares its not a real sig, just colored green)
Note**: If you want bigger triangles, Select a bigger sized document.
Sorry about the end result, I didnt think the green would be so bright...