A visualization must be easily understandable by everyone who sees it. This article demonstrates some ways to ensure that charts are understandable and engaging.
Chart elements like gridlines, axis labels, colors, etc. can all be simplified to highlight what is most important/relevant/interesting. You may be able to eliminate gridlines (Cole Nussbaumer, gridlines are gratuitous) or reserve colors for isolating individual data series and not for differentiating between all of the series being presented.
