BUT WAIT NOW I REMEMBER!!!
it's not just the mod. you have to use photoshop or a similar to edit the color pallet! you make it a grayscale pallet (black 0,0,0 to white 255,255,255) and then changes the bottommost color (white 255,255,255, I think) to orage or other color of your choice.
I hope it works. good luck and happy customizing! :p
Let me list all you need to make your own HL sprites - for hud, xhair or whatever:
create the image
- note its size in pixels must be the same as the original sprite you want to replace, as well as the picture(s) position(s). ** if it's not, then you will need to modify one or more .txt files located in half-life/valve(will vary if it's a mod)/sprites folder - but it's complicated to explain here. before saving your image, make sure the color mod is at 8 bits (if it's not turn to 8 bit, but I advice you the image may loose some quality). finally, save as a .bmp file and use sprwiz (may be easily found by googling) to create a .spr file. now to use it in game all you need to do is name it properly(if you changed no .txt then name as the .spr you want to replace) and drop it in your valve(or mod name)/sprites folder.
I hope I made it all clear. I'll keep an eye for your release. Success!