Learn how to publish a blob detection in 2D in RVIZ through markers : https://answers.ros.org/question/273792/hi-i-wanto-to-meake-a-program-that-give-the-position-of-a-red-ball-in-2d-with-rviz/

Q:Hi, i wanto to meake a program that give the position of a red ball in 2D with rviz

A: So here you have very rudimentary solution. Of course you will need to add calibration procedures, and take extra thing into account like the blob area to get the distance value, but this I hope gives you a starting point.

So essentially you need to publish a Marker topic , with a Sphere Type of colour red. This marker will have to be referenced to your camera link or similar. I’ve done this Video as an example of how it could be done.