have to admit I've never set fire to filament.
But the different chemicals that are used to make the different colours will most likely burn differently.
Probably wouldn't read too much into that.

Have you tried a different filament ?
I have one that simply won't work with my deltas, it happens.
At least that way we can rule out whether the machine has suddenyl developed an issue or whether it is definitely the filament.

Can't think of anything else worth trying.
Just get the cheapest white or black off ebay and see how that works.