phone cameras generally default to auto white balance which is good for snapshots, not so good for color accuracy
trying to get raw files out of phone cameras is not completely impossible, but the images are almost always processed into JPEGs
the main camera is going to boost saturation and contrast (make your image “pop”)
selfie camera is going to focus on “flesh tones”, so less saturation boost (or you look sunburnt) and less contrast boost (smooth out wrinkles and acne)
if you really want to focus on color accuracy over perceptual color, get hold of a gray card or color checker and plan on doing post-processing in something like Lightroom, Darktable, digiKam, RawTherapee or the like