Set gamma with pygame 2.0.x

I create a game and I would like to set the gamma of the screen. For example:

import pygame
from pygame.locals import *

pygame.init()
screen = pygame.display.set_mode((600, 450))
font = pygame.font.SysFont('consolas', 25)

red   = 1
green = 1
blue  = 1

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

    screen.fill((20, 20, 20))
    
    # draw colored zones
    for x in range(600):
        pygame.draw.line(screen, (x * 255 / 600, 0, 0), (x, 0), (x, 100))
    for x in range(600):
        pygame.draw.line(screen, (0, x * 255 / 600, 0), (x, 100), (x, 200))
    for x in range(600):
        pygame.draw.line(screen, (0, 0, x * 255 / 600), (x, 200), (x, 300))

    if pygame.mouse.get_pressed()[0]:
        x, y = pygame.mouse.get_pos()
        if y < 100:
            red   = x / 300
            pygame.display.set_gamma(red, green, blue)
        elif y < 200:
            green = x / 300
            pygame.display.set_gamma(red, green, blue)
        elif y < 300:
            blue  = x / 300
            pygame.display.set_gamma(red, green, blue)

    text = 'pygame.display.set_gamma(%.2f, %.2f, %.2f)' % (red, green, blue)
    text = font.render(text, 0, (255, 255, 255), True)
    screen.blit(text, (10, 440 - text.get_height())) # render the text

    pygame.display.flip()

But when I updated my pygame version to 2.0.0.dev6, the gamma correction didn't work, and I saw ugly colors, blue and yellow flashing irregularly.

I'm on Windows 10.

EDIT 1

After investigation, the green color seems not to be handled by the set_gamma function. When I change x value in the color (0, x * 255 / 600, 0), nothing happens.

EDIT 2

I now have the latest pygame version - now litteraly nothing happens.
According to the documentation,

Not all systems and hardware support gamma ramps

Ok! Maybe my computer doesn't handle this function! But:

if the function succeeds it will return True.

And I get True, even if nothing works as expected.
Does someone see clearly in this mess of bugs?