What does it mean to dream about blue?
Blue often suggests calm, distance, or sadness, and how you felt in the dream usually points to which.
Four ways to read it
Each reading below comes from a named tradition and a cited source, so you can see where it came from and decide what fits your dream.
Freud
Freud would treat a cool colour like blue as part of the dream's feeling-tone rather than a fixed sign. He might ask whether it carried calm or a quiet low mood, and what waking scene it belonged to. The colour borrows its meaning from what it colours.
After Freud, The Interpretation of Dreams (Brill trans., 1913), public domain.Jung
Jung linked blue to coolness, depth, and the realm of thought and spirit, the colour of sky and deep water. It can read as serenity or as withdrawal and sadness. As ever the mood of the dream and your own ties to the colour decide its weight.
Jungian concept (our summary).Modern
Under the continuity view, blue often follows from a calm or reflective waking mood, or sometimes a low one, the everyday meaning of feeling blue. It may also simply carry over a blue thing from your day. Begin with what the colour brings to mind for you.
Continuity hypothesis (our summary).Mythological
Blue was long the colour of the heavens and so of the divine and the eternal, painted on temple ceilings and the robes of sky gods. Because true blue pigment was once rare and costly, it also signalled the sacred and the high. In many traditions it shaded toward protection and the far horizon.
Rosmerta Publishing editorial synthesis (after Bulfinch; Brewer).