You can find two types of wall key holders among the downloads. For both, it is very important to make the size modification (scaling) so that both the car model and the holder and the key ring can be selected, i.e. both models should be modified together so that the size will be correct! When printing, you can print separately, even with different colors. For the colored model, there is still a twist in it that the color change settings depend on many things. The layer thickness, the scaling size. By default, the Prusa slicer usually suggests that this is a logo and automatically adjusts the layer thickness. This is a good starting point, but most settings are manual. If printing or assembling still doesn't work, contact me and I will be happy to help!