Edges of the “dots” inside are the same as edges “outside” – so you can’t fill them with color – they are cutouts in the glyphs.
It’s rather someone created misleading preview.
If you need to work with live text – it will be quite “complicated” to achieve what you are looking for.
But if you can outline your text – then you could use Pathfinder:
to remove them quickly from the copy, then place this copy underneath the original and then fill it with color.