A very very way to change ur unit color, i will making a dark archon as example.
First, go to Unit>Archon>Actor(Archon)>Event. (Or go directly to actor and search for archon)
Right click>Add event, OK>msg type change to "unit birth"; source name change to Archon (mine is Dark Archon).
Action: msg type change to "set tint color">pick a color (red or light red for our dark archon)>OK
Go to terrain, pick and drop ur archon and see it "turn" into dark archon.
"blend duration" define how fast the unit will change color.
U can use tint local to make an useful "color combine"
Speaking of tints and colors, does anyone know how to remove the Yellow glow from the Devourer Tissue Sample, when seen on the map in the editor theres no glow, but when seen in-game then theres a yellow glow I would like to get rid of. Any Ideas?