Colour ramps, in seven shapes. Linear sweeps across the frame, radial spreads from the middle, conic sweeps round like a clock hand, diamond and spiral do what their names suggest, noise scatters the colours into clouds, and four corners blends between a colour pinned at each corner.
Underneath, all of them work the same way. Each pixel is boiled down to a single number between 0 and 1 depending on where it sits, and that number is looked up along the ramp. The only thing that separates a linear gradient from a radial one is which question gets asked: how far across are you, or how far out.
repeat multiplies that number before the lookup, so the ramp runs through several times instead of once and you get bands. speed slides everything along, and because the number wraps at the end rather than stopping, the motion loops forever with no visible jump. Colours cycle in the order you give them and the last blends back into the first, so banded gradients have no seam.