So, you have an event coming up- and you know you want to use the perfect shade of plum. Sadly, that color is not available as one of the default colors in Word. Also, you can use the color selector, but how can you know that it will be the exact shade.
To create a custom color:
Select the fill tool , and from the pop-up menu, select "More Fill Colors..."
Click the custom tab, then enter the RGB numbers into the boxes.
Click OK, and the new color is now available to all the tools that use colors.