As you can see on the Picture, the crosshair is rendered under the pixel of the Stone Stairs. I found this on the Hypixel server.
[media]After that i tried it on a Singleplayer world. And for some reason, it didnt work there
[media]So i dont know, if this is a Minecraft Bug or a Hypixel Bug.
This is WAI, but what is happening? The crosshair inverts the color (or rather, value) to be the opposite of what its rendering over. The gray you're looking at is getting inverted from gray to gray, which means the colors blend together.