Meagan Longoria helps us choose a color palette for Power BI reports:
A color palette is simply a collection of colors applied to the visual elements in your report. What we typically refer to as color is a combination of three main properties: hue (base color on the color wheel), intensity (brightness or gray-ness) and value (lightness or darkness). You can build an engaging and professional looking report with just 6 colors. It’s possible to have fewer colors or more colors, but 6 should cover many common visualization needs. If you are using more than 6 colors, you might want to check that you are optimizing engagement and cognitive load.
Main color – default color on graphs
Color 2 – used when multiple colors are needed in a graph or report
Color 3 – used when multiple colors are needed in a graph or report and Color 2 has already been used
Highlight color – a color used to highlight important data points to make them stand out from other points on the page
Border color – a light color used for borders on tables and KPIs where necessary
Title color – color used for visual titles and axis labels as appropriate
There’s a lot of good advice in here.