The expression 'I'm changing' can mean that you're changing your clothes.

When the traffic light says 'I'm changing,' it means it is changing in color.

Another example of one of these riddles are

What did the salad say to the chef?

The answer would be

Don't look at me I' getting dressed.

The expression, I'm getting dressed can mean you are changing in clothes, as well.

But for the salad, getting dressed mean that sauce it being put in.

These kind of riddles are hard to understand.

If you get these riddles, you are very smart.......