Oops - my bad. I didn't read past the first couple posts. I should have noticed that you rendered it over white and still got red.

So yeah it's probably because you have a negative color somewhere.

Here's an alternative.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)