When a moderator deletes a question in Social Q&A, there's a prompt at the bottom of the window to ask if they'd like to Undo that removal. It can be easy to miss that prompt since it's mostly grey and black. But with a few simple lines of CSS, you can customize that prompt to stand out more. See the screen example below.
To set this up, visit the Admin (settings) area of your app and look for the menu choice called Branding & Custom CSS.
Carefully copy and paste the following lines starting with "div#" and ending with "}" and paste them into the box called CSS & Other Custom Source Code:
You can choose a different background color and/or text color if desired. The following code-selection website can be helpful to find and choose colors and determine the #hex code.