Actual violet (like UV LED or mercury lamp) should stimulate almost exclusively S cones. But it turns out that if you take blue, which stimulates M and L more than violet, and then add even more L stimulation, you end up with something that &quot;feels&quot; more violet than blue (at least to me). This is what bothers me. It looks like two distinct inputs producing the same output, even though there exists an intermediate input which produces different output.