Display Performance, Examined: Color Gamut
The 4S has a slightly smaller color gamut, but it's indistinguishable to the naked eye. We're only aware of the difference because we use a spectrophotometer (Spectracal-certified X-Rite i1Pro) to measure gamut performance.
The percentage of gamut rendered doesn't give us the entire picture. When we model the color gamut in 3D, we see that the 4S is slightly better at displaying red and blues. However, it's weaker in the greens compared to the iPhone 4.