There are an infinite number of fundamental colors, if by "fundamental" you mean "spectral". Spectral colors are also known loosely as rainbow colors. A spectral color is composed of a single fundamental color on the visible part of the electromagnetic spectrum, as opposed to a mixture of colors. Spectral colors such as red or green are composed of light waves of a single frequency. Non-spectral colors such as brown and pink are composed of a mixture of spectral colors. Simple lasers, by their very nature, only emit one frequency of light (to an excellent approximation). This means that simple lasers can only generate spectral colors (compound colors from laser systems can be made by mixing the light from several lasers, or by running the spectral color through a material that converts it to a mixture of colors). Even though the spectral colors are a subset of all colors, there are still an infinite amount of spectral colors. This fact becomes obvious when looking at the spectrum from a prism, which is simply a spread of spectral colors.