You would need to somehow read the texture.
There are posts about it. I’m not sure if anyone succeeded or shared their method.
https://forum.gdevelop.io/t/readpixel-for-layers/46724/3?u=keith_1357
Google claimed you could still read pixels if the opacity was zero. I tried it and you can’t.
But it gave me an idea. What if you put the image into a tiled sprite and made the object like 1 pixel. Then you adjusted the Offset to match the position of the cursor on an object. You then read that pixel.
It would be like having a tiny window showing the matching pixel. It probably wouldn’t even be that noticeable. A bit like a dead pixel.