What you will need:
Ch2r, by XIU (Link)
Photoshop, by Adobe (Link)
Possibly the BitmControl.dll I attached, if Ch2r scrambles the image
Possibly the DDS Plugin I attached, if Photoshop can't open the image
If niether of the above work, get the full Ch2r I included.

Tutorial:
• Open Ch2r
• Open mainmenu.map
• Navigate to ui/global_bitmaps/emblems (Pic)
• Double-click foreground.dds
• Select a bitmap, I will use 57 (The number three) (Pic)
• Click Extract
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• Open the foreground.#.0.dds in Photoshop (Where # is whichever you extracted), Select "No" to Use MIP Maps
• Edit to your liking, make it like the original colors, blue is primary, yellow is secondary. (Pic)
• Resave it as a 4:4:4:4 ARGB (16 Bit) and select Generate MIP Maps (Pic)
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• Go back to Ch2r
• Go to the foreground bitmap viewer
• On the drop down list, select Old Bitmap Viewer (Pic)
• Go back to the same bitmap you extracted (57 for me)
• Click Inject, find your image

If it worked, you should see "Image sucessfully injected" or something to that effect.