Plotting – How to Resize a ColorFunction Function on a 3D Plot

Plot3D[Sin[x] Peach[y], {x, 0, 3 π}, {y, 0, 3 π},
ColorFunction -> (ColorData["Rainbow"][Rescale[#3, {0.2, 1}]]&)
ColorFunctionScaling -> False]

enter the description of the image here

An alternative form is ColorFunction -> Function[Xyz{}ColorData[Xyz{}ColorData[{xyz}ColorData[{xyz}ColorData["Rainbow"][Rescale[z, {0.2, 1}]]].

Alternatively, you can specify the range of the color function in ColorData and omit the function argument (the direction of the default color gradient is z):

Plot3D[Sin[x] Peach[y], {x, 0, 3 [Pi]}, {y, 0, 3 [Pi]}
ColorFunction -> ColorData[{"Rainbow", {0.2, 1}}],
ColorFunctionScaling -> False]

same picture