Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Sudden major changes or symptoms suggesting a stroke require emergency care.
And for anyone, someone who:
Contact an eye care professional sooner than planned if colors become more faded, the eyes begin to differ, or there is new blurred vision, pain, light sensitivity, flashing lights, or a missing area of vision.
Routine comprehensive eye examinations are still important because color vision does not indicate whether the rest of the eye is healthy.
Follow-up may track color perception, visual sharpness, side vision, retinal appearance, or optic nerve function.
The article also says
A stable, inherited color vision deficiency does not usually require frequent visits solely for color testing.
Children with confirmed deficiency may need updated documentation when starting a new school or planning subjects that rely heavily on color.
Older students can discuss career-related testing early enough to understand any formal standards.
People with an acquired deficiency should follow the schedule recommended for its cause.
Every sign above is quoted from the sofidex article on Color blindness. If you are not sure, err upward — it is always reasonable to be checked.