There is currently a series of rolling rail strikes in France. The dates are scheduled in advance and can be found by entering the phrase, "French rail strike dates" into your search engine. You don't state when you are traveling, so this may be the best way for you to have current information.
The rail strike is a bit different than some strikes you may be familiar with in that some trains do run. It is not the total cessation of service, but a reduced service. I would definitely buy my rail tickets in advance for the best pricing. If the train ends up being cancelled due to the strike, you will be free to travel on any other train that is running that day or be eligible for a full refund.
There is also the option of taking Flixbus from CDG to Colmar.