POLYGON

command

Draw a closed polygon (at least 3 vertices). An optional fill colour paints the interior.

POLYGON x1, y1, x2, y2, x3, y3… [, colour] [, fill]

x, y - vertex coordinates (at least three pairs) colour - outline colour (optional) fill - fill colour (optional; last arguments)

Example:

POLYGON 10, 10, 40, 10, 25, 30, RGB(255, 0, 0)
POLYGON 10, 10, 40, 10, 25, 30, RGB(255, 0, 0), RGB(128, 0, 0)

Source: docs/help/polygon.txt inmmcore. On the computer, typeHELP POLYGON.