[Multi-View] Consider suggesting people to color axis title for dual axis chart

[kanitw]

like in https://vega.github.io/vega-lite/examples/layer_dual_axis.html

The current example in the notebook doesn't make it clear which variable is which mark

(It's ok for people who follow the tutorial as they created it themselves, but once they copy this example to create charts and share with other audience, it would be confusing.)

[RandomFractals]

tbh, I still find those dual Y axis graphs confusing and bad data viz practice for typical consumers. github Traffic/Visitors tab/graph is a prime example of it, but I second @kanitw suggestion to color code them if you must.

[domoritz]

Yep, they are generally considered an anti-pattern (and @kanitw is well aware of that) but there are some useful cases and you definitely need to make sure there are hints for what the lines/bars mean by coloring the marks and the corresponding titles.

[RandomFractals]

agreed! good catch @kanitw!