Data viz: additional docs needed for color usage

[aagonzales]

Based on a conversation in slack we do not document the following data visualization decisions well on the website currently:

• Data vis modules can only have a white or black background for accessibility contrast. No other background colors are allowed.
• Charts should have a white or black border between data sets to help with contrast.
• Tabular representation for accessibility

[thyhmdo]

Mike G.'s comment on the same thread

The problem in a nutshell: with more than a few colours, it is impossible to create colours where each colour both contrasts 3:1 with the background AND contrasts 3:1 with each other colour.
Obviously there are ways to overcome this on a design basis: include persistent labels on your data points, for example. But that’s not very scalable or practical on anything but a simple chart. Assuming this is an interactive chart (and not just a image capture of a chart), the answer is that the legend on Carbon charts is responsive and offers a number of options. As well, if the user uses a mouse on a desktop computer, tooltips provide textual information that reinforces the data sets.

Screen.Recording.2024-07-24.at.2.42.39.PM.mov