If you would like to create a fill-in-the-blank type worksheet quickly and easily within a Google Doc - simply use the CLOZEit Add-on for Google Docs.
Once added, you can highlight or underline words you'd like to be blanked. It does not matter what color you use to highlight the words.
Once you launch the Add-on you will see the options available to you on the right-hand side (see image below).
You can the Add-on multiple times. If there are more words you wish to be blanked, select them and run it again. You can also edit the word bank list.
Embedded below is a 2 minute and 21 second YouTube tutorial.