You can use the gradient tool
I just found it. It's under "Styles" but I'm using a blue background and it fades it but turns it purple.....It's probably something I'm doing wrong. It's been since 2020 and I'm re-doing some covers. I appreciate your suggestions.
Perhaps you are not familiar with the Gradient Tool. Here is a HelpX article with the basics.
Here I was able to use it to recreate your background.
As with most features in Elements there are several ways to create this effect. Another way would be to create a Fill layer with the gradient.
First, you need to choose the colors for the gradient. In this case - dark and light green.
Do the same for the light green shade by clicking on the Background color in the Color Picker (currently white in my screenshot).
The Color boxes will now look like this:
Huge THANK YOU for the alternative. I'm still learning things all the time.