Comment 6 for bug 166622

Because you need RGB to save color to SVG. You can't store
HSL. SVG does not allow you that. So whenever an HSL value
changes, it is converted to RGB and saved. Whenever you move
focus or selection, it reads RGB back and converts to HSL to
update the sliders. So when you fiddle with it it goes
HSL->RGB->HSL->RGB etc.

Please do the experiment as I described, this will make it
more clear if it's only conversion or we have some other
problems with it (such as low precision).