RGB Histogram
Three separate histograms, one per colour channel, revealing clipping that a combined luminance histogram would hide.
In depth
The luminance histogram weights the channels the way human vision does, so a fully clipped blue channel barely moves it. Saturated colours clip one channel long before overall brightness looks excessive, which is why product, flower and stage photographers work exclusively from the RGB view.
Examples in practice
Stage lighting in saturated magenta clips red and blue while the luminance histogram still shows comfortable headroom.