I don't know, but note that the raw, unadjusted images are no more "authentic" than the color-adjusted ones.

Mastcam uses a Bayer RGB matrix, very similar to a consumer digital camera. Effectively, each "pixel" of the matrix has an R, G, or B color filter in front of it. I don't know the specific wavelength response of each filter, but it's likely to be very close to a high-end consumer camera.

This is different from (e.g.,) Hubble images, which (a) are captured through non-RGB filters, and (b) use long exposures far beyond what a human eye would see.