In theory, yes, but in practice, probably only in relatively limited numbers.
Both Britain and France quietly concluded that that while their empires could supply a number of high quality, long standing volunteer units, using colonial conscripts would present very serious reliability problems. France, more desperate than the UK both geographically and demographicaly, may have resorted to some coerced enlistments with say ethnic Algerians but stopped short of conscription.
By late 1917 most men from the empires inclined to volunteer had already done so and recruitment campaigns by France and Great Britain were falling well short of the number of desired enlistees.
France did conscript large numbers of people from their colonies, most famously West Africa, and the 1918 recruitment campaign in West Africa alone not only fulfilled its objective of 50,000 recruits, but it exceeded it at 63,000, without any resistance in the territory. A lot of troops, and materials from the colonies couldn't be put to use because there was insufficient shipping available because it was needed to ship the Americans over, so if the Americans weren't participating in sending land troops to Europe, even if colonial recruitment campaigns didn't increase at all, there would be more troops available. And since surely the Americans must be supplying
something to the war effort, be it money or arms (in contrast to OTL when the French were producing arms for the Americans on loan). Colonial soldiers not being able to be shipped due to insufficient shipping weren't the only ones either, the Portuguese for example were prepared to send additional troops to France, but insufficient shipping was available.
Perhaps these soldiers would have been less effective than the Americans (which I'm not sure of, but I presume it would be the case or otherwise they would have been shipped instead of the Americans), but they would still enable quiet sectors of the front to be garrisoned, just as the Americans did.
Interesting PoD.
And Imo one point that has significance has not yet been raised. Namely the French reaction of an USA DoW without troops in Europe. And that amidst the troubles that they had in 1917...
So how will France shore up its flagging morale to keep on fighting for longer then Germany when Imo they faced a serious crisis in OTL and were helped out by the prospect of American Meat for the Grinder.
Tell them they aren't planning to attack any time soon (as OTL), improve conditions (as OTL), and give them some sort of lie that the Germans will be broken by a blockade and that they don't need to attack. Historically Petain said they were waiting on the tanks and the Americans, so emphasize tanks even more to soldiers. The soldiers were historically willing to continue in defensive operations, but objected to further offensive operations. Perhaps morale is shakier than originally, but if need be the French can go without the spoiling offensives they launched after the Nivelle Offensive.