To adjust colors used in your chart, select your chart (one click) and expand the “Color” dropdown in the right sidebar. There you will be able to choose color for each data variable by using the color picker or entering a hex code. NOTE: switching to a different color theme in the right sidebar will switch all colors in all charts/objects in your project and provide a list of template-matching colors to choose from.
You can also enable the “Use one color” option > select a color > and hit “Apply to all” to use a single color for all data entries.
To change colors used in chart's legend and axis, expand the Fonts tab in the right sidebar.