I was wondering if it is possible to get the automatically assigned color of a line series, or the legend symbol color in RGB.
The colour used for the legend symbols is pulled from the series.style that the symbol is representing. You might be able to figure out which property on the style is the one you're after just by having a look. If it's not obvious then feel free to post here the type of series you are using and we'll be able to let you know exactly which properties the legend synbol is read from.
Yeah, I get the color via the lineColor property (since I was using LineSeries). I eventually found out that in order to get the color from the series, it must be retrieved in/after sChartRenderFinished:.