Luc's way is exactly how to do it. (Well done, sir!)

These colors are buried in the color scheme now so people won't choose them
inadvertently. It used to be a problem when people would want to change the
hyperlink colors, they'd end up with all kinds of other objects changing
colors, too, because the hyperlink and colored hyperlink colors could be
used (pretty much had to be, actually) for anything. And they were right
there in your face, just waiting to be applied to all kinds of objects, too.

So now, they hyperlink colors really are reserved for hyperlinks. They show
up where you edit theme colors, but they don't show up in the color pickers
where you apply colors to stuff on your slides.

Also, each theme color scheme has two light/dark combinations. If you use
the "background styles" for your slide backgrounds, this ensures that
whether you switch to a light or dark background in the background styles,
your text will switch, too -- so it's always visible. AND all accent colors
(and, by extension, hyperlink colors) are designed to show up on any of the
four light-dark colors. It's really kind of cool.

Just wanted to toss that out. I find it interesting and actually, I think it
was a good design decision.