Converts the NDScopePlotChannel color parameter to a hashable representation.
The NDScopePlotChannel as_tuple() method combines the channel name and parameters into a tuple. The hash of this tuple is calculated in the hash method. Since lists are not hashable this fails if the color parameter is given as a rgba list in a scope template. This merge request addresses this by converting the rgba list to a hashable representation.
Closes issue #249 (closed).