Red is selected, which gives you a red vertical bar. Select H (hue) and you will get a multi-colored bar. Click through all of the options - H, S, B, R, G, B and observe the changes.
You either have your Project set to 16bit or you have changed the default color value in the Info Panel to 16 bit. I use decimal because I write a lot of expressions and do a lot of 16 and 32-bit projects and it's easier to work with the same values that color properties work with.