FWIW; I purchased a bunch of Cephalotus seed last fall from Stephen Morely, some of which were "EB x self". They are now roughly 1 year since I planted them. The EB x self are showing a lot more colour than any of the other seedlings, and all are being grown beside each other under the same...
As corky said, Dave has mentioned twice that anthocyanins haven't been found in Nepenthes. Im sure if this discussion was brought up on the PP forums he could find an article or two.
I tested 4 in water, 4 in soaked LFS and 4 stuck horizontally in the top of my Cephs pot. Soaked LFS rooted fastest 100%. Ones in the Ceph pot look good about 2 months later. The ones in the water, 1 rotted away within a few weeks, the other 3 have multiple roots.
For me, soaked LFS or putting...
Ive had perlite get that blackish color on occasion and it never seemed to cause any trouble (see pic below). Never had the rotten egg smell in my Ping pots though. If you're worried about it I would repot and skip the top dressing of sand. Most Pinguicula never skip a beat when being repotted.
All the above suggestions are good, but here is a few more similar threads on the subject.