Sundogs and 22-degree halo fragments are the halos seen most often. Which of the two wins the race for appearances depends on locality.  A hundred miles or so can alter their relative frequency.

In mid to north Europe a sundog might be visible 2-3 times a week and they are as common in parts of the USA.

Not all are bright and obvious. Many will be a transient smudge of colour. To find the less obvious ones measure distance from the sun with an outstretched hand held at arms length. With the thumb over the sun a sundog, if present, will be at the same altitude and near the tip of the little finger.

The colours are never pure spectral. Like this one, they might show occasional greens and blues but they are subdued because all their colours except the extreme reds are overlain with others..