Changing Styles Dynamically

element.style.backgroundColor = '#ff0000';
element.style.backgroundColor = 'rgb(255, 0, 0)';
element.style.backgroundColor = 'red';

Hexadecimal (#ff0000)
RGB/RGBA
RGB/RGBA format is often most appropriate for dynamic color manipulation because it's easy to parse individual components, interpolate between colors, and adjust opacity independently. While hex codes are common in static CSS, RGB values are more intuitive for programmatic changes. HSL can be even better for certain animations as it separates hue, saturation, and lightness, making it easier to modify specific aspects of a color.
Named colors
HSL/HSLA