Well, can do it the color expert way and use spectral data. (I don't pull actual chips until the very end of my process and we're ready to go buy samples)
Where you see the biggest difference is in redness and yellowness. Sculptors Clay is closer to the YR (orange) hue family, has more chroma, and is lighter and brighter than Revere Pewter. Chroma meaning Sculptors Clay is more colorful and not as neutral as Revere Pewter.
Revere Pewter can shift depending on the light and look purple, blue, green or even blue-green. Sculptors Clay has the potential for peachy overtones and could shift and look purple.
I don't have a Colorography done for Sculptors Clay but this illustrates what hue, value, chroma and LRV looks like on a scale.
