Color themes
The overall color theme of a chart can be set with ColorTheme property. Setting the theme will override majority of the object colors in the created chart. Therefore, every manually assigned color will be lost in the Visual Studio property grid without a warning. It is advised to first set the ColorTheme and then modify the individual object colors.
chart.ColorTheme = ColorTheme.SkyBlue; // Changing the color theme

Two color themes. On the left, default Dark theme with some custom colors. On the right, Aurora theme.
Custom themes
LightningChart allows creating custom color themes by updating CustomDynamicTheme -property. There are two ways to do this. Either get the custom theme to a variable and update that, or set ColorTheme to CustomDynamicTheme option and update its properties.
// Method 1
ThemeBasics theme = _chart.CustomDynamicTheme;
theme.BackgroundColor = Colors.Black;
theme.ChartTitleColor = Colors.Green;
_chart.CustomDynamicTheme = theme;
_chart.UpdateCustomTheme();
// Method 2
_chart.ColorTheme = ColorTheme.CustomDynamicTheme;
_chart.CustomDynamicTheme.ChartTitleColor = Colors.Green;
_chart.UpdateCustomTheme();
Some themes use automatic coloring for axes and series. To manually set axis or series colors, disable MultiColorAxis or MultiColorSeries respectively, then set the colors.
ThemeBasics theme = _chart.CustomDynamicTheme;
theme.MultiColorAxis = false;
theme.AxisColor = Colors.Blue;
_chart.CustomDynamicTheme = theme;
Examples
Interactive Examples demo application has ThemeCreator example, which allows investigating the color themes and creating new ones.