This should either be "rgb(0, 0, 0)" or "rgba(0, 0, 0, 0.1)". However, based on the default value it should be the latter.
### Colors
-When supplying colors to Chart options, you can use a number of formats. You can specify the color as a string in hexadecimal, RGB, or HSL notations. If a color is needed, but not specified, Chart.js will use the global default color. This color is stored at `Chart.defaults.global.defaultColor`. It is initially set to 'rgb(0, 0, 0, 0.1)';
+When supplying colors to Chart options, you can use a number of formats. You can specify the color as a string in hexadecimal, RGB, or HSL notations. If a color is needed, but not specified, Chart.js will use the global default color. This color is stored at `Chart.defaults.global.defaultColor`. It is initially set to 'rgba(0, 0, 0, 0.1)';
You can also pass a [CanvasGradient](https://developer.mozilla.org/en-US/docs/Web/API/CanvasGradient) object. You will need to create this before passing to the chart, but using it you can achieve some interesting effects.