If it's too far off but you really want that color, they do still have that color in their Essentials (cotton) collection. The downside is that eventually the cotton will fade more than the poly, but supposedly dying technology has improved to extend the amount of time before the cotton noticeably fades if well cared for.
I usually do a different colored thread in my borders anyways but I make kids quilts where that's more desirable. If you really can't find anything, I'd do a hard break at the border's ditch & go with a duller version of the color so it kind of fades away into the border rather than drawing more attention to itself.