My main build is largely comprised of monochromatic stone in different forms, however despite being indicated to have the same colour in the block description, there are clear discrepancies when placed in the world. I wonder if it has anything to do with the reflectiveness of different block types and lighting?
yes, indeed - each type of blocks in a line of crafting for example (rock>>stone>>refined etc.) have different properties if it comes to absorbing/reflecting light and such; thus the same color ends up looking a bit different when applied to different blocks
Reflective blocks like refined stone also tend to be heavily tinted by the sky color (even when indoors)