legend colour not visible #5

• In the screenshot attached below the lowest category is 0-252 and the hex colour is #f7fbff this is too light and not visible.
• This can noticed with colours green, blue, greys and red

Expected Behaviour
The colour used to represent the lowest range in the legend be visible on the chart.

Actual Behaviour
The colour used to represent the lowest range in the legend isn't visible on the chart. Probably a darker shade could be used

Basic Information
kibana version: 6.4

Screenshots