What color distribution does a protoplanetary disk have?
The answer seems to be a clear &quot;it depends&quot;:

Homogenity of the disks depends on the age of the protoplanetary disk.
Temperature is a function of the radius and the color-scale used in (old) artists' impressions is indeed correct.

On Wikipedia on the topic there is a gallery of different observations, also in the visual spectrum. An impressive picture of the density fluctuations within the protoplanetary disk is provideded by the Disk Substructures at High Angular Resolution Project (DSHARP) as explained e.g. by the ESO.
Edit Remarks following a suggestion by Rob Jeffries:

Please note that the DSHARP images are not from the visual part of the spectrum.