Hi,
I don't think that it is something you can correct within JMP. Your destination application probably misinterprets the pasted image. Could you have pasted the image as a Vector format (SVG or equivalent)? Vector images are notorious for replacing colors.
If you are working on a Windows system with Office, you could try pasting the graph as Picture Enhanced Metafile, which tends to produce the sharpest images with the least issues.
If you are on Mac, you will need to explore copy/paste methods to yield the best results.
Let us know if this helps.
Best,
TS
Thierry R. Sornasse