I was trying to get a multi pass Material ID to export for photoshop. I need it to select all Objects with the same material at once. I used multi-pass->mask->ID-> Materials. I used 2 different materials for my objects and pressed render, but somehow the multi pass Material ID didn’t work, as all objects had the same color, even tho they had different materials.
When creating your second materials did you copy the first material and adjusted that? Because that way the material will have the same color when you do a Id based on material.
If you create a new materials for the second material and apply that you will get a different color.
Or you can try a different mode then material. I always do material, instance and object to have more choice. Or you can add specific masks with material ID numbers but that’s more work.