Are all electromagnetic radiation in the optical portion of the electromagnetic spectrum: visible, have the same wavelength, have the same frequency, or all three?
Well, if you are speaking about the visible portion of the electromagnetic spectrum, then yes, the colors of the visible spectrum are all visible. How else could we see the color? Red, orange, yellow, green, blue, indigo, and violet, memorized by using the "Roy G. Biv" mnemonic. But wavelength and frequency are not the same for all the visible colors. Instead, these are the very things that make the separate colors what they are. Red is the longest wavelength, followed by orange. It progresses all the way up to violet, which is the shortest wavelength. Wavelength determines frequency, which is the number of waves that pass per second, which is usually expressed in hertz. So being visible is a definite "yes", while having the same wavelength and frequency is a most decided "no". Most decidedly not all three.