why am getting two different expressions from the same effect control

You cannot simply tie color to a slider. Sliders have one property. Color has four. That's why you get the four temp values. The person who created the tutorial you are watching did not link color to a slider. Something else must be going on, or you are watching a tutorial prepared by an amateur, and they cut something out. 

The only option for a color expression is to use one of the color conversions and supply the appropriate values or simply enter the color array. When applied to a fill property, this expression will give you a yellow color.

[1, 1, 0, 1]

 That's all there is to it. If you want to pickwhip from a color property to a color controller, add an Expression Controls/Color Control. 

In the future, when you are having problems with a tutorial, please post a link to the tutorial so we can see what you are seeing. If you are trying to change colors with an if/else statement, you need to use an Effect/Expression Controls/Menu Control, not a slider. I suspect a funky workflow from the instructor.