I saw this double sun-dog tonight. My cheap camera couldn’t really cope with this difficult light but you can at least make them out – the bright spots to the left and right of the sun. They are always the same height and, when there is a pair, always equidistant from the sun.
The left hand dog is the stronger and you can see the colours better in this one
The effect is caused by sunlight reflecting off ice crystals. They are always red-coloured on the side facing the sun with the colours getting cooler the farther away they are.