Is it necessary to use American English in the SAT/ACT and College Application essay?

In India we typically use British English while writing; for example, colour instead of color or humour instead of humor. Which style do we use while writing SAT/ACT essays and college application essays on the CommonApp?

I'm a student from India and I'll be applying to US universities in a few years. Thanking you in advance.

SAT and ACT essays do not penalize students for spelling issues unless the issues make it difficult for readers to understand what the student is trying to say, so British English is perfectly fine.

For college application essays on the CommonApp, things are a little murkier, as individual schools may have different policies. Your safest bet is to contact the admissions offices for the schools you're applying to and checking with them, but the next best thing to that is being consistent in your use of British or American English. Attempting to change your essay to American English but leaving in a "favourite" instead of "favorite" will look worse than all British English.