Most colour blind people are able to see things as clearly as other people but they are unable to fully 'see' red, green or blue light. There are different types of colour blindness and there are extremely rare cases where people are unable to see any colour at all.

Why is blue colorblind rare?

Many of the genes involved in color vision are on the X chromosome, making color blindness much more common in males than in females because males only have one X chromosome, while females have two.

Is color blindness a disability?

About Colorblindness/Color Deficiency

Although considered only a minor disability, slightly fewer than 10% of all men suffer some form of colorblindness (also called color deficiency), so this audience is very widespread. Colorblind users are unable to distinguish certain color cues, often red versus green.