Thanks dog I finally figured out how to do it. You need to click on the object then on create and edit gradients button then on the gradient point then the color edit dialogue will be opened.

I spent around a hour trying to figure it out, got a headache literally and still not a single clue. I basically want to:
1. Get the #XXXXXX colors of "7012-661-145-733-759-865-745" gradient.
2. Change its general color to gray.
How do I do it?