How to make canvas cleaner?

I’ve worked as a barista for 5 months ish now and I’ve been working on latte art. The “canvas” (I think it’s called?) always looks like this and I usually don’t see that in other lattes. Is there a way to make it more even in colour? I try to pour the milk high and wiggle it a bit. Do I need to go higher. Thanks for any help 🙂