preview fill selection with color

How is a selected portion of an image filled with color of my choosing. The instructions found said to open the "format sidebar".

After searching the inter-webs I found no other reference to the format side bar in preview so I'm wondering if you can help me find out how to fill a space with color.

Here is the image with a space I'm trying to fill with color. Even though you cannot see in this image, the pink space is selected, using the Instant Alpha tool. So, selectiing the space is not my problem. Problem is I don't know how to change it's color except with color adjust, which does not offer an obvious way to select a color to put in there.

It might be hard to tell but there is a portion of this map filled with a sort of pink color. I want to pick a another color that is more distinct how is this done?

Any information you can provide toward this answer will be much appreciated thank you