nivo supports theming via the
theme property, this property
must contain an object which defines various styles to be applied to your
charts. If you don't provide a theme, the default theme will be used. When
you provide a theme, you don't have to provide all properties as it will get
merged with the default theme.
There are a few things to notice while theming your components. Values for font-size, borders… are unitless as nivo supports several implementations (SVG, HTML, Canvas), however you can pass extra CSS attributes when using a specific implementation, for example, you might add a stroke-dasharray to the grid lines when using the SVG implementation of the Bar component, however it will have no effect on BarCanvas as it doesn't support it. The theme only drives the base style of the charts, for things such as symbol colors, patterns, legends, you'll have to use the dedicated properties.