Legend/popover colour chip update for column chart

Problem

From discussion here: #614 (comment 364661865)

• The color chip in the legend/popover doesn't really match the columns in charts
• It's hard to recognise that you can actually click chips in the legend to show/hide values in chart
• It's current hard to differentiate between lines and columns on the same chart: #615

Solution

Legend/popover colour chip update for column chart

Style as described here: #617 (comment 370810027)