You can put pinkBackground
in additional CSS Class, then you will have to add the following code into your Additional CSS, Dashboard > Appearance > Customize > Additional CSS.
.pinkBackground {
background-color: pink;
}
Keep in mind you should use the hex code in order to be able to set a specific color, so in this case, you can use the hex pink which would be background-color: #ffc0cb;
.