Change the color of a sale sticker
After:

Before:

Code:
/* -- code to change the background sticker color for sale products -- */
.sticker--sale {
background: #FFFFFF !important;
color: #111111;
font-weight: bold;
}
/* - end - */
Notes:
You can use any hex color value. The code here is a white background: #FFFFFF; and black text color of #111111;
Additional hex colors: http://www.colorhexa.com/web-safe-colors
Where do I add the code?
Use this link to learn where exactly to add this code snippet: