How do I find all of one color in a line drawing and replace it with another color?

Greetings, I'd like to replace this goat-puke green color with "black."

I have tried everything, but can't find the right command. I'm sure that nothing could be easier, but I'm stumped and will probably smack myself in the head when I see the answer.  lol  Please help.

Cheers. - Frank

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