I had some left over red and orange BC that I'd put in the freezer and defrosted and added some fresh white BC so I could add more red-red to darken it for a cake I'm doing tonight. I've added more than enough Wilton Red-Red and No-Taste Red to deepen the colour, but it's still this light, coral-type colour.

What the heck am I doing wrong (besides using Wilton instead of Americolor ) and how do I fix it?

Any possibility that you added icing whitener before you froze it and forgot? I've done that with fondant and it would not take colour no matter what I did. Finally remembered what I had done and tossed it all! Otherwise, maybe it just needs to sit overnight and deepen. Hope it works out for you!!

Hmmm... I may have, but I don't think so. I've only started using the white white in the last couple cakes I've made, and I think I'd frozen this stuff before that.

I did colour it this afternoon and it's now at least 4 hours later and it doesn't look darker yet. I'm afraid to just use it and hope it darkens... Think that's just my best bet? I don't have time to make more.

I've been in a position where my red didn't darken enough and I already had it on the cake - It was still a very bright pink (on it's way to red, but not quite there). Before I added any other elements, I sprayed it with Wilton colour spray (I don't have an airbrush). It worked just fine. Maybe a quick trip to Michael's will help you out! They also carry Duff's colour spray - I've tried the silver and it didn't colour well at all, so I'd stick with Wilton.