Landscape photographer Melvin Nicholson captured this stunning shot of a ghost rainbow, aka white rainbow or fog bow, in Rannoch Moor north of Glasgow, Scotland.
Like rainbows, fogbows are caused by sunglight reflecting off water drops. However, as NASA explains:
The fog itself is not confined to an arch — the fog is mostly transparent but relatively uniform.The fogbow shape is created by those drops with the best angle to divert sunlight to the observer. The fogbow's relative lack of colors are caused by the relatively smaller water drops. The drops active above are so small that the quantum mechanical wavelength of light becomes important and smears out colors that would be created by larger rainbow water drops acting like small prisms reflecting sunlight.