rose-coloured glasses
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ROSE-COLORED GLASSES: "Some unfortunate people never take their rose-colored glasses off, but everyone wears these spectacles occasionally. This attitude of cheerful optimism, of seeing everything in an attractive, pleasant light, has always been with us, while the expression itself goes back to at least 1861, when it is first recorded in 'Tom Brown at Oxford': 'Oxford was a sort of Utopia to the Captain.He continued to behold towers, and quadrangles, and chapels, through rose-colored glasses." From the "Encyclopedia of Word and Phrase Origins" by Robert Hendrickson (Facts on File, New York, 1997)
for some reason i've heard rose-tinted lenses more often, but maybe i'm just a freak.