A couple of notable points.
The test will do a couple of things to make sure everything is working, then time how long it takes to compare 2 colors a load of times.
You can get the test code and class from gitHub. It's been put there automatically - you can use Getting started with VbaGit to pull it into your workbook or just download it. Rememer to look at the dependency file for the Excel references required.
Learning Apps Script, (and transitioning from VBA) are covered comprehensively in my my book, Going Gas - from VBA to Apps script, All formats are available from O'Reilly, Amazon and all good bookshops. You can also read a preview on O'Reilly