Highlighting weekends on a chart

Are there any UX rules for adding noise to a chart? I know that Stephen Few and his ilk talk about reducing chart noise as much as possible. But Is it acceptable to add some in?

The use-case I'm thinking about specifically is highlighting on a timeseries when the weekends occur. When looking at lots of time-based data, there are often dips on the weekends due to lower use compared to weekdays.

Here is an example: https://jsfiddle.net/zwLneos6/