First of all, you need to determinate the color palette that you'll use for that project.
To determinate color palette, you need to pay attention to a few things:
- What is the brand color
- What's your product about
After you form the color palette you should follow few rules in terms of action colors.
Your color palette should be divided into three main (could be more) sections.
- Warning (Alert) Colors
- "GO" colors
- Neutral colors
Warning colors are usually picked from the red palette.
e.g., CANCEL, DELETE, QUIT, etc.
"GO" colors needs to create user's feeling of moving forward.
e.g., CONTINUE, APPLY, AGREE, etc.
Neutral colors are defining "an extra features".
e.g., MORE, EDIT, POST A COMMENT, etc.
Difference between these types of buttons should be obvious.
Should you use opposite colors?
Depends on your style.