import sys
import pygame as pg

pg.init()
screen = pg.display.set_mode((1024,768))
clock  = pg.time.Clock()
mstate = 0

while True :
    for event in pg.event.get():
        if event.type == pg.QUIT:
            pg.quit()
            sys.exit()

    mclick=pg.mouse.get_pressed()
    if mclick==(0,0,0):
        clock.tick(30)
        mstate=0
        continue

    mx,my=pg.mouse.get_pos()
    if mstate==1:
        cc=(255*mclick[1],255*mclick[0],255*mclick[2])
        pg.draw.line(screen,cc,[px,py],[mx,my],1)
        pg.display.flip()

    mstate=1
    px,py=mx,my