Providing two different values for interlacedColor is not available as of now. You can create a stripLine starting from viewPortMinimum to viewPortMaximum which would act as second value for interlacedColor. Please, take a look at this jsFiddle.
We have backgroundColor that covers whole canvas. But if you need background color just to cover the plotArea, you can use striplines as a work-around for now.
Background color for plotArea is in our roadMap, but we don’t have any timeline for it yet. Thank you, for suggesting it though. I’ll forward it to my other team members.