The 3-level (not '''bits''') RGB uses three level for every red, green and blue color components, resulting in a 3<sup>3</sup> = 27 colours palette.
A notabble specificity of the Amstrad CPC palette is that it offers only one "Grey".
Compared to the C64 with...er...only greys..? (Humor inside)
This explains why in some games rocks and stone are coloured in other shades to get a good colour layer with more than 3 shades (black, grey and white).
Notable exemple : [[Defender of the Crown]] with Purple rocks and stone walls...
Also it is also notable that this palette has a "lot" of Blue and Green variations...it is possible to use a mode 0 screen with almost only16 pseudo Green and Blue colours (yet a bit purple for some of them).
Many graphist used only coloured flashy bold colours as it was often reproached but other 8bit fans (C64...).
But a clever choice in said colours could also give good results too in Pastel shades.