How to duplicate the values of variable in pavlovia?

Description of the problem:
I got the Warning message on the Runner like this.
→ WARNING duplicate variable names: colorChange, startColor

Those variables are as shown below.

The $StartColor is from white to black(grayscale), simple. I think it is not a problem.

And this is the contents of code component.

I wrote the codes like in matlab, and it works well in the PsychoPy Builder.
But in pavlovia(online), the color of circle just stays black.
No change, Can’t bring another StartColors.

My goal is making the color of circle change over time.

What should I do? Do I need to make another code for changing the method?

Version of mine is 2021.2.3.