Where can I find direct experimental evidence that Snell's law is correct for at least three of the typical spectral colours (say RGB). Thank you.
May I ask why exactly you are asking? This is a trivial exercise performed in many places, including my undergrad labs last year. If I still had my lab notebook I could show you the data.
In any case, I'm not exactly sure what you're looking for. The refractive index for most of the visual spectrum is known for essentially every type of glass in existence. You should be able to find the appropriate values in many places. Is that what you're looking for?
Where can I find experimental evidence that Snell's law is correct about the different degree of refraction that each colour experiences when passing through a prism (medium) beside that in which the purporting experiments use the colours dispersed from a beam of white light to extrapolate the premise.