This has already been implemented. Note that this is a breaking-change. Previously you would set two attributed string snippets on DTLinkButton. This API was changed. Instead you get an image of the glyphRun in normal and highlighted state and you set these images on the UIButton.
Implemented in 7224445
You can set the hyperlink active color via a:active or via passing DTDefaultLinkHighlightColor with a color name or DTColor in the parsing options. Note that you still need to provide a custom subview for the link, see DemoTextViewController for an example implementation.