Find a hexadecimal value for a number with the calculator in Windows 7.

background-color: rgb(142, 142, 142);

 
 

This, in CSS, specifies a color without a hexadecimal value. You may also specify the amount of opacity in this manner. In the following example we are using thirty percent opacity.

background-color: rgba(142, 142, 142, 0.3);

 
 

...but hexadecimal is better! In the calculator that comes with Windows 7, go to "Programmer" under "View" then type in 142 and finally click "Hex" to get: 8E.