Even in normal experience the brain is being stimulated. So theoretically, you wouldn't need eyes to experience color. You would only need to replicate the physical properties at the onset of brain activity. Those are called neural correlates of consciousness. However, there's the byproduct as the result of that activity, the experience associated with it. If reality is fundamentally material, there are two possible implications: (1) the very experience itself is physical. That is, the inherent experiences of smelling, or tasting, or seeing a color, in themselves have to be physical. The challenge with this is that we don't know the nature of that physical property and we have no evidence for it (besides counting consciousness itself as evidence, which is begging the question). (2) There's also the view that, rather than the correlates causing the experience, they are the experience. The challenge here becomes to demonstrate which correlate maps to exactly which experience (and not another). Neither of (1) or (2) have been successfully demonstrated.
It is true that neither 1 nor 2 have been successfully demonstrated, but there is quite a double standard here: you claim that idealism has the answers to questions about the mind, but you have not shown it explaining anything. Deducing the reality of idealism from the absence of answers to 1 or 2 is exactly like saying, in 1950, that as biology has not identified the biochemical correlates of cell reproduction, life must be fundamental (I know some people hold this view today, but it is at best a niche view that generates little controversy in either philosophy or science.)
https://en.wikipedia.org/wiki/Neural_correlates_of_conscious...