Hi,
There is a re-enactment unit:
http://delanceys.org/
Unfortunately, the site isn't terribly helpful on the dates of the unit's uniform changes, but this link and the one immediately below will give you contacts who might be able to give you a definitive answer.
http://www.royalprovincial.com/reenactors/groups/2del.shtml
This next link is to a deserter report that appeared in NYC in March 1779.
http://www.royalprovincial.com/military/rhist/delancey/deldest1.htm
You will see that the man is wearing a regimental coat lapelled green - this means it would almost certainly have been a red coat, as the corps wore green-faced-white up to 1778, then red-faced-green from 1779-1782, and red-faced-blue only from 1782 to the end of the war. For a man to be wearing a red coat in March 1779, it would most likely have had to have been issued the previous year, or at the very least the item would have arrived in America during mid-/late-1778, as merchant convoys generally didn't cross the Atlantic between late November and late March, due to the weather. The two battalions sent to Savannah didn't leave NYC until December 1778, so my opinion (and that's all it is at the moment) is that they would have received their new uniforms either just before heading south, or very soon afterwards.
I suspect that's not really what you wanted to hear.
Cheers,
RtL