I am creating lower thirds for a video, and would like the change the color of the rectangle I created. I can't seem to get the color selection to come back. I keep clicking on the shape and it is not giving me the option of editing the color. How do I get it to come back?
With your solid selected, you can hit the keyboard shortcut ctrl+shift+y (or cmd+shift+y on Mac) and it will bring up the solid settings dialog.
Or select the layer, go to Layer>Solid Settings in the menu.
Assuming this is an After Effects question, that is. I see that this post was moved out of the Color management forum, so if this is a Premiere question, the answer is very different.
Alternatively, if you think you'll be tweaking the color multiple times, you may find it easier to apply the "Fill" effect to the layer, which will give you an easily-accessible color picker in your Effect Controls panel/by twirling open the layer effects. (Or, depending on your needs, you could also use the "Color Overlay" layer style in the same fashion.)