"In one of the windows [Frodo] caught a glimpse of a sallow face with sly, slanting eyes; but it vanished at once.
'So that's where that southerner is hiding!' he thought. 'He looks more than half like a goblin.'"
(The Fellowship of the Ring, Chapter 11, A Knife in the Dark)
"But there were some others that were horrible: man-high, but with goblin-faces, sallow, leering, squint-eyed."
(The Two Towers, Chapter 9, Flotsam and Jetsam)
"When they reached The Green Dragon, the last house on the Hobbiton side, now lifeless and with broken windows, they were disturbed to see half a dozen large ill-favoured Men lounging against the inn-wall; they were squint-eyed and sallow-faced.
'Like that friend of Bill Ferny's at Bree,' said Sam.
'Like many that I saw at Isengard,' muttered Merry."
(The Return of the King, Chapter 8, The Scouring of the Shire)
While the subjects in that third example are described as "Men," it's likely they are half-orcs, since they're said to be like Bill Ferny's friend, who's the one being described in the first quote as "more than half like a goblin."
Furthermore, Tolkien, in a letter he wrote to Forrest J Ackerman in 1958, described orcs thusly: "The Orcs are definitely stated to be corruptions of the 'human' form seen in Elves and Men. They are (or were) squat, broad, flat-nosed, sallow-skinned, with wide mouths and slant eyes: in fact degraded and repulsive versions of the (to Europeans) least lovely Mongol-types." (This is reproduced in The Letters of JRR Tolkien; it is letter #210.)