How can test colour picture tube of TV?

To test the color picture tube of a TV, use a color test pattern or a DVD with test images that include various colors and gradients. Observe the display for color accuracy, brightness, and contrast, looking for any distortions, discoloration, or flickering. Additionally, check for proper convergence of colors by viewing edges where different colors meet. If issues are found, adjustments may be needed, or professional repair might be required.