SETFLOODCOLOR color
SETFLOODCOLOUR color
SETFC color

Sets the flood color to color, which can either be a color index or a color vector. A color index is a number from 0 - 15. A color vector is a list of [red green blue] intensities, each in the range of 0 - 255. For an explanation of the color input, see the section on Using Color.

The flood color affects the FILL and BITBLOCK commands.

Filling with a square with lime:

CLEARSCREEN
REPEAT 4 [FORWARD 100 RIGHT 90]
RIGHT 45
PENUP
FORWARD 20
SETFLOODCOLOR "Lime
FILL

Using variables in a color vector:

MAKE "red   100
MAKE "green 100
MAKE "blue  100
SETFLOODCOLOR (LIST :red :green :blue)