I have several instances of VEP (Vienna Ensemble Pro) connected to Studio One. I've colored the channels in the mixer based on the instrument types, but the colors disappear after a couple days. At first I thought it was due to an instance of VEP being "disconnected" (a setting in the VST, not in S1), but that isn't the case. As far as I can see it's random, other than the fact that multiple channels lose their colors at once, and others don't. See this screenshot for an example of what it looks like after it happens. All of the channels had colors, then suddenly several don't. The strings instances were disconnected temporarily. But that shouldn't affect the color as the VST is still loaded. And at very least, it shouldn't affect the colors of any other instance. It appears to be a bug.
ASUS X99-A, i7 5820k, Win10 x64, Studio One v188.8.131.52707
RME HDSP AIO, Driver 4.14 (latest, pub. on 1/29/2016)
Note: I am using VEP to host instruments on 2 additional machines.