It can become confusing, since we let you rename and move the default column, which is the default if you are new to a particular project's Workboard. I think these also used to be darkgrey ?
Currently the default workboard column can not be changed. You can work around this by doing a rename + drag a bunch of tasks around cycle. The work around isn't terrible but this has independently confused just about every team here setting up workboards for the first time.