Instead of blue and pink shouldn’t and Xline partial repaints be into the generic Xlines charcoal so can they can be easily moved around next time the wind changes?

I usually do a Flickr search when you guys mention fleet numbers as I don’t know them like you do.
It seems some of these Wright deckers have been in Castles Express livery, blue Xlines, Corporate AND yellow Xlines?
And didn’t the X21 just get its current allocation (“B5s”?) within the last year or two as they were deemed more suitable for the route, (or it’s previous “Streetdecks” were required elsewhere)?

Would someone mind listing the timeline of X21 allocations please to remind me why things were moved around and partially repainted so much, (just post Presidents)?