All of the above are good ideas and methods.
Also give a thought to the time frame of your model Is it fresh out of the factory? Just been on a road trip over: muddy,dusty, wet, dirt,grass, forest? all would have an effect on the handles.
The age of the tool brand new; well used; through a battle? will be a factor.
All this is to say that a combination of colors can be used to represent the handles. some quite light (ie new) vs very old/used (darker/stained??)
Regardless you can't go very wrong. If you need some ideas look at the tool section of a hardware store, tools you or a neighbor may have in the garage; look at the ones on the back of yard maintenance trucks
Have Fun!