Please describe more details about your scenario. We will appreciate it if you post a screenshot.
Do you create shapes in your visualization using Power bi Desktop? If that is the case, you can click the shape and format the shape using the following options, you are able to change fill color, font color and so on.
Thanks, Lydia Zhang
Community Support Team _ Lydia Zhang If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.