It's yellowish, but it doesn't seem to color the whip. I put it on w/ an old (but clean) rag.
(I notice a bit of color come out of my whip on the rag, but mine is a whiskey-tan IOAB, so results may vary on that point.)
Generally, I hear that you can (or should) pecard the fall after each use. Pecard the main body of the whip (thong) anywhere from a few times a year to monthly, I believe, based on how much use it gets and under what conditions. After you do it once, you'll be able to see the difference between your well-treated whip and what it looks like dry.
Most whips, I hear you shouldn't treat the handle or large knots, for fear of loosening them up too much. Just a light surface amount IF IT NEEDS IT. (On the IOAB this doesn't seem to be an issue, though.)
Okay, whipsters, how wrong did I get that?

(Harry, I'd wait for more answers to get a consensus before you go w/ my advice, in case I bungled something. But I believe that's it.)
J