If you need to change button colors or menu colors, follow these steps:

Change Button Colors

Go to Avada → Options → Avada Builder Elements → Buttons

Scroll down until you see:

1. Button Gradient Start Color
2. Button Gradient End Color
3. Button Gradient Start Hover Color
4. Button Gradient End Hover Color

You will notice these two are the same:

1. Button Gradient Start Color
2. Button Gradient End Color

And these two:

1. Button Gradient Start Hover Color
2. Button Gradient End Hover Color

The reason is to keep the button a solid color and you need to change those four options to globally change your buttons.