Adding Custom Color options to “Highlight Color” Toolbar Option

I am wondering if there is a way to add custom colors to the Highlight Color Toolbar Option. None of the colors there are good for me. I want MS Word style light grey (#eeeeee) and yellow (#ffff00). I don’t want to have to manually type it in each time.

I am new to web development and blogging, so I am sorry if this is outside the scope of your plugin. I have gotten so well used to MS Word over the years, and I would prefer to keep those sort of ‘luxuries’, if you will.

See image below.
https://ibb.co/mBb25Yw