Rash kinda thingy

Heya so I’ve had this rash kind of thing pop up once in a while for the past few years. It only comes for about a day at random times and random places on my body throughout the year. It doesn’t itch or burn ,in fact I can’t even tell it’s there unless I look. It’s not raised (or crusty) and it can’t be washed off. I don’t use any special lotions or body washes. It almost looks like watercolor painting haha

Has anyone experienced the same thing or know what it is? It’s not bothersome, I’d just like to know what it is! Thank you in advance!!