Gazebo has its markers, too. And... though I can not believe it myself...
looks like... you can not change colors for them!
Also, it is not very elegant in the first place:
This was a single marker, sticking out of the ground... I am not going to use this approach anyway.
Using objects instead of markers is kind of an obvious solution
(to "can not change color" problem). Just an important moment
here:
An object should have "static" property, so that physics engine
doesn't spend time on it.
Here is an example:
And here is the URDF for this "marker" (I just took an existing URDF, I am not going to use this approach as it is ugly):