As per the info at Patch 7.4.0.2987 - Colorweave Festival - New Worldboss
I'd like to point out that this location is used during the main zone questline, and the location for this new boss could impede progress.
Most world bosses are in 'out of the way' locations, so questing players can proceed without being needlessly attacked.
Now, I'll admit to having not yet encountered the boss, so don't know if yellow or red...
- If yellow, this wouldn't be a problem as the questline can continue around her.
- If red, she'll attack anyone coming near - even those who are just following the questline to get to the next zone.
Now, as I've said, I've not seen her yet, so I may be bleating on about nothing...