Font Color on Envelopes?

I have a question about the font color on out outer and inner envelopes. I'm addressing them on my computer and printing them at home.

FH thinks the font should be black on the outer envelope...he wants to keep it simple. Which I'm ok with.

But my invites are white with sage green lettering. What color should the font be on the inner envelope? Black to match the outer envelope, or sage green to match the invitation??