I,m always looking for a way to reduce draw calls particularly for simple objects that maybe scattered around a scene. Here is one little trick I sometimes use :
The cube on the left (Cube in the inspector) has six draw calls - one for each material on each of six faces. The cube on the right (Cube.001 in the inspector) has only one draw call and uses a very very simple texture from this palette collection turned into a 16x16 pixel texture with GIMP. (See image below)
The trick comes with the UV mapping. Select each face in Blender in UV editing mode, select all the pixels in the UV window for that face, then S-> =0. You will get a dot of four vertices - now move them to the colour of choice.Repeat for each face. Now you have six colours on the cube right cube, but only one draw call. No multi-materials!
Stay Safe All, gryff
The texture I used used 16x16 pixels - if you can see it - about 1kb download