I think this is a interesting idea that I've put a little thought into so here me out, what if iron golems were affected by the biome they were in? I feel like an example is the best way to explain it.
Say you were currently in a tundra and planned to stay there awhile. You built an iron golem to keep you safe from strays and whatever else might be lurking. But over time your iron golem starts to change. He gets rusted from the snow and scratched from the winds blowing ice and snow towards him. You think one too many blizzards couldn't do that right? Either way you bring your iron golem inside and decide you are ready to move.
You are now in a plains near the badlands. You make a new iron golem because your other one seems weaker than before and you feel bad. You decide to go adventring after a little while. You come back to find your new iron golem covered in grass stains and ridden with flowers. You take him to your farm to care for the plants. You decide to do an experiment to see what keeps happening to your iron golems. You make a new iron golem and take it to the badlands. He must get affected somehow right? So you take him there and build yourself a little house with some materials and wait. Sure enough your new iron golem is orange by the morning.
You decide to clean him off and take him home. Maybe it's best to just keep your golems inside you think.
Sorry it was so long. But if you like the idea or think of some things that could improve it please tell me!