Wavelength and frequency are proportional to each other. The speed of light is 299,792,458 meters per second. 299,792,458 meters can be divided infinitely, so that there are infinite wavelengths and infinite proportional frequencies, and hence infinite colors. Unfortunately the human eye sucks as a frequency and wavelength meter.
299,792,458 / .000000400 = 749,481,145,000,000
So a wavelength of .000000400 meters (which is 400 nanometers) has a frequency of 749,481,145,000,000 which is a frequency of 749 TeraHertz.
It works the other way too:
299,792,458 / 749,481,145,000,000 = .000000400
or…
.000000400 x 749,481,145,000,000 = 299,792,458
Since wavelength x frequency must equal the speed of light then there are infinite combinations of wavelength and frequency that equal the speed of light.
So yes, there are infinite colors because there are infinite wavelengths and infinite frequencies.