Blew is the past tense of the verb blow: "The wind blew the fence over." Blue is the colour, and by extension a low mood: "She painted the door blue." They sound identical, so the only guide is what the word is doing in the sentence — an action, or a description.
The core difference
Blew is a verb form and nothing else. It is what blow becomes in the past: blow, blew, blown. Blue is an adjective or a noun — a colour on the spectrum, a shade of paint, a feeling of sadness.
Using blew
Every use of blew describes something that already happened.
- "A gust blew my umbrella inside out."
- "He blew out the candles in one go."
- "The referee blew the whistle."
- "We blew the budget on the kitchen."
The last two show blew in idioms, which is where writers hesitate. "Blew it" (failed), "blew up" (exploded, or lost their temper), "blew off" (skipped) and "blew away" (impressed) are all the verb, all spelt with the W.
Using blue
- "The walls are a soft blue."
- "Blue skies all week."
- "He's been a bit blue since the move."
- "The news came out of the blue."
"Out of the blue" is the phrase most often misspelt as "out of the blew". It refers to a clear sky, so it takes the colour.
The test
Try replacing the word with a different past-tense verb — threw is a good stand-in because it rhymes and behaves the same way. "A gust threw my umbrella inside out" makes sense, so blew is right. "The walls are a soft threw" is nonsense, so you want blue. Alternatively, swap in green: if the sentence still works, the colour is what you need.
The memory trick
Blew keeps the W of blow — the verb hangs on to its consonant, just as grow becomes grew and throw becomes threw. Blue ends -ue like hue, and a hue is a colour. Verb keeps the W; colour rhymes with hue.
The edge case
Watch "blew over" against "blue" in weather writing, where both are plausible: "the storm blew over" (it passed) has nothing to do with the sky's colour. And note blown, the third form: "the fuse has blown", not "has blew". If there is a have, has or had in front, you need blown, never blew.
One more: blues, the music and the mood, is always the colour spelling — "she sings the blues", "a case of the Monday blues".
Frequently Asked Questions
Is it 'out of the blue' or 'out of the blew'?
"Out of the blue." The phrase pictures something appearing from a clear blue sky, so it takes the colour. "Blew" would make it a past-tense verb, which the sentence has no room for.
Is it 'the wind blew' or 'the wind blue'?
"The wind blew." You need a verb to say what the wind did, and blew is the past tense of blow. "The wind blue" reads as though the wind were a colour.
When do I use 'blown' instead of 'blew'?
Use blown after have, has or had: "the tyre has blown", "they had blown their savings". Use blew on its own as a simple past: "the tyre blew on the motorway".