Yes, colleges will accept either ACT or SAT results whenever they are taken. Some students take these two test as 10th graders, but most students take the PSAT- the preliminary SAT at that grade. In fact, some states actually pay for all 10th graders to take the PSAT.
I strongly encourage you to take the PSAT as a 10th grader but in answer to your question, those scores count if you want to submit them to a college when you begin applying for college as a senior.
I recommend contacting the admissions office of the college(s) you are interested in attending. Every college has different requirements, and an admissions advisor can best answer your questions for the college they represent.