I make a dotted map just like the one on the image below. I am using Illustrator and Photoshop.
How can I select and re-color some of the dots on this image?
In Photoshop, select one of the dots with the Magic Wand tool, then choose Select > Similar. This will select all the dots.
Use Layer > New > Layer via Copy to make a new layer from these dots, then in the Layers Panel, click the checkerboard icon next to the word Lock. This will prevent painting from leaking out of the dot area.
All you have to do now is to choose a colour, switch to the Brush tool and select a hard-edged brush, and paint the dots on the new layer. Only the dot area will be coloured.