After accidentally pressing Ctrl-R in Chrome instead of Shift-R typing up this message and losing all my work, I'm retyping this in somewhat abbreviated form...

After some months off of this hobby, I upgraded from FPP 2016.51 to 2017.30 64-bit.
I'm adding a MegaTree this year and while fiddling around with some effects, I noticed that when the screen showed Green, my sample pixel string hooked up to my controller was Red. Similarly, Blue on-screen lit up my pixels Green, and Red on-screen lit up my pixels Blue.
My megatree's start channel is 8193 for Red, 8194 for Green, and 8195 for Blue. Checking in FPP's test mode and turning on the individual channels, the colours work out okay.
Checking out xLights test mode, I found out that in order to turn on the first pixel of the tree, I need to turn on 8509 (xLights labels it as supposed to be Green, but my pixel glows red), 8510 (Blue turns Green), and 8511 (Red turns Blue).
I was scratching my head on the channel shift, and then realized that I have a USB DMX dongle in my Setup tab that had 316 channels reserved for it (yeah, it's a weird number), and 316 is the difference between 8509 and 8193. Well, when I delete the DMX dongle from the Setup tab, my pixels display the correct colour. However, I need to keep my DMX dongle for my show.
Is this a bug that was introduced since 2016.51?