As investigating the project we have found out that it have special slots "layers" - overlapping spacial slots. So what happens is that when resizing the browser the rendering of the ScheduleView is called,
its layout is updated and the special slots are recreated and that leads to one slots shown above the other. So as it might seems like the colors are changed, but actually the slots are moving one in front of the other.
So what you can do is change the special slots in order to make them not overlapping. Other possible solution would be to set Z index to the different special slots, unfortunately this is not available yet and we have it logged in our Public Issue Tracking System as a feature request. Here
you can track its progress.
Hope this would help.
the Telerik team