See the Scratch Maths Copybook 3 page 47. With Scratch code it is as easy to fill a circle as to draw its circumference. Switch the order of the pen down/ pen commands in the repeat loop. The Pie Chart fills a circle in 4 colour segments. Each segment is a fraction of 360°. This can be achieved using a maths algorithm to indicate the number of repeats in the loop that draws each segment. Set the pen colour of the segment in each for each repeat loop.
The drawing is instant when in TURBO MODE is on (See the Edit Menu or Hold SHIFT while Clicking the Green Flag). Set the radius length and click the Draw button.