if you were the "old bearded russian intellectual from the 1800s" kind of anarchist, then yeah
but pretty much all organized anarchist groups in practice have used some variety of black or black/red flag
Red (Pre October Revolution) and then Black (post October Revolution) pure anarchy
Black/yellow is AnCap
Black/Orange is "market socialism" anarchy/"muatulism"
Green/black "green" anarchism
Blue/black individualism anarchist (what? Outside of anarchy-communism, anarchy is full individualism..)
Dark green/black "Egoist" anarchism
Grey/Black Some sort of "All interactions are by choice" crap
White/Black anarcho-pacifism (hah damn fools)
Dark Blue/Black Anarcho-Transhumanism (we should go Deus Ex with human modifications)
Then a whole bunch of fetish/gender identity Anarchism with different colors.
but wouldn't Federal agents coming into Portland be from the decision of those in state power? In the same way that states have been calling in the national guard?
Not really the portland rioters have been targeting federal buildings (The US Federal court more often then not), the Feds don't need the states premission to enforce federal law nor to defend federal property. They also have been pointing lasers at federal officer's faces/eyes this is legally assault of a federal officer (lasers can fuck up your eyes).
There is also a good chance that the people being rounded up by the mini vans have been engaged in more then just the riots (from what I recall a few weeks ago some rioters were arrested ended up having pipe bombs)