Instructions on how to use the map with MS Paint, courtesy of Dutch Anon.

How do you fill in the map? It's very easy. You only need to use two buttons, which I have circled in red.
Say you want to colour a specific region light red, you click the tool that I marked B, and you'll see your cursor takes the shape of that tool. Then you left click the colour you want to use, i.e. the big circle. You'll notice that colour 1, which I marked C, changes to light red.
If you repeat this process but you RIGHT click a coloured circle instead of left clicking it, you will select the colour as colour 2. Let's click dark red. This way you can have both shades of red selected at the same time, which makes colouring in the map more convenient, especially when doing big countries.
Now you select the tool which I marked A. Let's get to colouring. Say you want to colour Indiana in light red and you want to colour Ohio in dark red. Easy. Left click Indiana and right click Ohio.