I'd like to think the difference is not because of the skin color but due to the fact that Ukraine is fairly well integrated into the west even if it is not part of the EU/Nato, and the fact that it's a fairly developed country with lots of cell phones which provides tons of first hand unofficial coverage on social media.
At least that's what I'd like to believe.
Its that and that other thing.
The private sector is rather giddy and anxious to get Ukrainians into the work force, its an easy fit, where as our Syrian brothers and sisters in general has a steeper curve. Add to that that someone has been cultivating the far right segment in Europe too and the sad fact is, that yes, color plays a factor, it is gasoline on some scheming vile segments in politics, and as a clinical calculus, to avoid our own 2016 moment, we must act accordingly.
I am 100% certain it was Putins plan as well, with Syria, one reason for the demolition of civilian structures was to create a refugee stream right into the alt-right-neo-fuckery engine that he has spend sooo much money cultivating.
So yea, color is a thing, what is not a thing is saying "hey its color" and everything snaps back into place... Its a big complicated machinery involving hostile foreign actors.