UPDATE: I just posted a newer version that uses patterns instead of objects. It’s simpler and easier to adapt to any map size.
Colorable hex grid overlays in various sizes. If you have a map larger than any of the sizes, just chain them together. They should snap to grid well enough, or you can turn off snap to grid and line them up manually.
I recommend turning off shadows before placing the grids, and I recommend putting them on their own map level.