I remember hearing that dreams are always colourless, and that we subconsciously add the colour in, while recalling the dream.
However, I have become sceptical. Why would it be impossible for us to hallucinate in colour? Also, what if the dream was significantly based on the presence of a colour?
For example (and this is what stirred up the thought), I had a dream where a notable portion of it was consumed by the adoration of someone's blue eyes. I remember thinking about the colour of the eyes, during the dream. When I think about it now, I remember the blue. Perhaps during the dream the eyes were labelled 'blue', but the blue wasn't visualised or remembered until awakening?

Are dreams really colourless? Explain.