Change the color of a sold out sticker

Example:

Code:

/* -- code to change the background sticker color for sold-out products -- */
.sticker--sold { background : #cc0000 !important; }
/* - end - */

Notes:
You can use any hex color value. The code here is a red background: #cc0000

Additional hex colors:  http://www.colorhexa.com/web-safe-colors

Where do I add the code?

Open your Code Editor. 

From your list of themes, find the Actions link for the theme you'd like to edit. Then select Edit code. Example draft theme:

Example if you're working from your main live/published theme:

Quick link if the theme is live/published:
Open Code Editor

Next, in the Code Editor find your theme's CSS file, this will vary depending on which version of Pipeline you're running:
Which version of Pipeline am I using?

Once you know your version, find the right file in the left Assets folder:

Pipeline 4 - If you're working with a draft theme, open this file:

You'll be opening this file:

assets/theme.scss.liquid

Quick link if the theme is live/published:
assets/theme.scss.liquid

Or

Earlier versions of Pipeline - If your theme is older than Pipeline 4 open this file for draft themes:

You'll be opening this file for earlier versions of Pipeline:

assets/style.scss.liquid

Quick link if the theme is live/published and an earlier version of Pipeline:
assets/style.scss.liquid

Add the code to the very bottom of the file on a new line after all other code. Make a couple blank lines before pasting the code snippet. 

Example:

Save the file after adding your code.