Which preposition to use with coppery

at Occurrences 1%

The first day he was away was dreadful sultry; the sun went down away over the woods in a kind of a red-hot fog, and it seemed as though the stars were dull and coppery at night; even the whip-poor-wills was too hot to sing; nothin' but a doleful screech-owl quavered away, a half a mile off, a good hour, steady.

beyond Occurrences 1%

So, with mind both busy and absent, Kurt Dorn harrowed the fallow ground abandoned by his men; and when the day was done, with the sun setting hot and coppery beyond the dim, dark ranges, he guided the tired horses homeward and plodded back of them, weary and spent.

in Occurrences 1%

On the first occasion I saw a small, sturdily built man, with a big, clerical sort of face with marked features, and, as far as I can recollect, rather coppery in hue.

Which preposition to use with  coppery