Hey there! Not a silly question, coding is a pain to comb through. :) The green gradient is located in in a few places because the panels aren't transparent (oops, that's not the most efficient way to code this baby): right below !--LEFT SIDE--, right below !--RIGHT SIDE--, and then after every "a name" section. If you do a search for #182107, it'll highlight these places - the code looks like this:
All you need to do is change #182107 to any color you want - and you can do it in one fell swoop by using a Find/Replace option in something like Notepad. :D