I.e. my chef friend had ground jalapeno at her apartment, shit was good. Like cayenne level heat but with a different flavor
I had to go to like an international food market to find some near me which is weird given how ubiquitous jalapeno peppers are
Other considerations aside, natural dyes are notoriously fickle things so it's going to come down to what else the sumac gets mixed with.
Probably the most relatable example of this is if you ever used red cabbage juice as a pH indicator - those changes in pH make a huge difference to the colour that the juice shows.
I wouldn't be at all surprised if sumac imparted a deep red or purplish colour in enough concentration (when in the right situation - e.g. sumac lemonade) but I've never seen za'atar turn dough or labneh or vegetables an unusual colour so idk. I'm no expert and I've never looked into it deeply but I am a sumac aficionado and I'm handy in the kitchen so make of that whatever you will.