The sun's size appears to change throughout the day due to atmospheric effects and the Earth's rotation. When the sun is low on the horizon, it may appear larger due to the optical phenomenon known as atmospheric refraction. This is caused by the bending of light as it passes through the Earth's atmosphere, making the sun appear closer and larger. However, the actual size of the sun remains the same.

Regarding its colour, the sun's colour can vary depending on several factors:

Solar Flares and Activity: The sun emits flares, prominences, and sunspots, which can result in variations in its colour and brightness. During periods of high solar activity, the sun can appear brighter and have a more intense yellowish or orange hue.

Time of Day: The colour of the sun can change throughout the day. At sunrise and sunset, when the sun is low on the horizon, it often appears red or orange due to the increased scattering of blue light by the Earth's atmosphere.

Atmospheric Conditions: The Earth's atmosphere, including factors like dust, water droplets, and pollution, can affect the colour of the sun. For instance, during heavy dust or smoke conditions, the sun may appear to have a reddish or hazy appearance.

While these factors can cause apparent changes in the colour and brightness of the sun, the actual physical characteristics of the sun remain largely constant. Its true colour is often described as white or yellow-white.

It's worth noting that directly looking at the sun without proper eye protection is never recommended, as it can cause serious damage to the eyes.