Ice is transparent; snow is a mass of crystals
A clear ice crystal does not have a white pigment. Fresh snow looks white because it is made of many tiny ice crystals and air spaces. Light entering the snow is repeatedly reflected and scattered at boundaries between ice and air, then redirected in many directions. The mixture of wavelengths reaching our eyes is perceived as white.
How crystal structure changes the view
A single snowflake can be translucent, but a field of snow contains an enormous number of crystals in different orientations. That arrangement makes it difficult for light to travel straight through. The Met Office explains that snow’s appearance comes from the way its ice crystals scatter light, rather than from a white colouring agent.
Snow can also appear blue or grey in deep shadows, and dirty snow may look brown or yellow. Those colours reflect lighting, depth, surface conditions or material mixed into the snow. The familiar bright white appearance is strongest when the snow is relatively clean and illuminated by broad daylight.
Why this matters for weather and safety
The same scattering that makes snow bright can make it harder to judge contours and distance during a snowstorm. Flat light reduces shadows, while falling snow limits visibility. Drivers and pedestrians should slow down and use appropriate lighting in these conditions; the surface can also conceal ice, uneven ground or obstacles.
So the short answer is that snow appears white because its many ice crystals scatter visible light. The crystals themselves are not painted white, and changes in illumination or contamination can change the colour we see.