meshstack_spherepack2.gh (17.8 KB)
As a quick way using only existing components without scripting, you can also simply create a stack of coloured meshes (or rather a single disjoint mesh).
It should be fairly quick to make a new goal that would let you actually input a grid of points and values though for if you need also vertical interpolation of values instead of just closest in a discrete sampling as happens with this mesh stack approach. It could also optionally include collision with a boundary mesh, for if you wanted the spheres inside the volume, instead of just their centers inside.