They are used solely in the test. And the test does the SCSS compilation and compares the results to expected files. So changing anything in the test source SCSS and we need to change the expected results too ! This isn"t necessary...
But there were some confusions as the css/light-grey.scss file is modified very often, and one of the test source file has the same name !
Adding the prefix DO_NOT_CHANGE should avoid such errors in the future O:)
