Contrast is very important to colour-blind people: to prevent loss of information carried by colours or misunderstandings, developers should design mock-ups in grayscale and choose colour palettes and opacity options based on the preliminary results of online contrast checking tools. Ensure contrast ratio of text blocks is at least 4:5:1, except for very large texts, purely decorative images or backgrounds or parts of brand names or logotypes. Do not design contents in a way that is known to cause seizures or physical reactions, especially to people with cognitive impairments or specific sensitivities (synaesthesia, epilepsy, etc.)