The = pileus = is wood brown to fawn, clay color or isabelline color.    From Wordnik.com.  [Studies of American Fungi. Mushrooms, Edible, Poisonous, etc.] Reference

Cinereous above, white below; the colour varies from pure ashy grey to grey with an isabelline tinge.    From Wordnik.com.  [Natural History of the Mammalia of India and Ceylon] Reference

Fur long and full, pale, sandy mouse-coloured above, isabelline below; pale on the well-clad limbs, and also on the tail laterally and underneath.    From Wordnik.com.  [Natural History of the Mammalia of India and Ceylon] Reference

All the birds, reptiles, and insects of Sahara, says Canon Tristram, copy closely the grey or isabelline colour of the boundless sands that stretch around them.    From Wordnik.com.  [Falling in Love With Other Essays on More Exact Branches of Science] Reference

To begin with, all the smaller denizens of the desert -- whether butterflies, beetles, birds, or lizards -- must be quite uniformly isabelline or sand-coloured.    From Wordnik.com.  [Falling in Love With Other Essays on More Exact Branches of Science] Reference

I made the following notes regarding them: Fur very fine, close and silky, rufescent brown, more rufous on the head, isabelline below; feet flesh-coloured, hinder ones large, much larger than those of the.    From Wordnik.com.  [Natural History of the Mammalia of India and Ceylon] Reference

General colour sandy, more or less mixed with dusky; pale isabelline on the sides; no grey on rump; tail dark brown above; ears without black tip; lower parts white; fur soft and long; fore-legs very pale, brown in front; hind-legs still paler, brown outside.    From Wordnik.com.  [Natural History of the Mammalia of India and Ceylon] Reference

Pale sandy brown; almost isabelline on back and sides; rump greyish-white; tail black above; face and anterior portion of the ears concolorous with back; terminal portion of ears black outside at the edge; breast light rufous; lower parts white; fur fine, close and soft; fore-legs in front, and hind-legs outside, with a light brownish tinge.    From Wordnik.com.  [Natural History of the Mammalia of India and Ceylon] Reference

Hence, without exception, the upper plumage of every bird, whether lark, chat, sylvain, or sand-grouse, and also the fur of all the smaller mammals, and the skin of all the snakes and lizards, is of one uniform isabelline or sand colour. ".    From Wordnik.com.  [Darwinism (1889)] Reference