Add "No color" option to "Background Color" and "Font Color"

Steps to follow to reproduce:

• Create a new document and go to wysiwyg edit mode
• Write some text
• Select text and make text background yellow and font color blue
• Try removing the background color without removing the font color and vice versa

Result: You cannot clear one formatting without clearing all formatting

Suggestion: Add "No color" option to "Background Color" and "Font Color"