CANVAS:stroke_rect(x1, y1, x2, y2, color)

Stroke a rectangle outline defined by the bounding area of x1,y2 to x2,y2 with a specific color. The width of the outline is the last value passed to CANVAS:set_line_width or 1 if no width has ever been specified.

    x1      The x position of the first corner
    y1      The y position of the first corner
    x2      The x position of the second corner
    y2      The y position of the second corner
    color   An RGB color value as an integer value.

-- Draw three colored outlines across the canvas
function StrokeRGB(name)
    local canvas = gre.get_canvas(name)
    local size = canvas:get_dimensions()
    local rw = size.width / 3
    canvas:stroke_rect(0,    0, rw-1,   size.height, 0xff0000)
    canvas:stroke_rect(rw,   0, 2*rw-1, size.height, 0x00ff00)
    canvas:stroke_rect(2*rw, 0, 3*rw-1, size.height, 0x0000ff)