I'd do both with a simple Colorize in post. The first one is all the same color. The second one requires a bit of Selecting, first for the Colorizing of the letter, then invert the selection to Colorize the background. 2 minutes tops.
Just have a try.
1. Change green to yellow with color correction/balance tool.
2. Use curves and levels to adjust the image exposure.
3. Colorize the image.
4. Make a selection to refine the letter.
Heck here I've been doing it the hard way all this time by getting Gold Member to come over to my studio and pee on the set to get the gold color I wanted.