Are third-party crosshairs allowed to use or will it get me banned?

It's a shame that custom crosshairs are not a built in feature. I usually prefer to have a striking pink crosshair in games like Counter Strike and Overwatch. But size/shape options should be put in too. And on a per weapon basis ideally.

Pink is not my favourite colour by the way. I neither know nor care why that pink haired lady was picked as my avatar. But at least it stands out, like my crosshair normally does.