A fuller version of the quote is:
There was an inn in the trees at the Bains d’Alliez where the woodcutters stopped to drink, and we sat inside warmed by the stove and drank hot red wine with spices and lemon in it. They called it gluhwein and it was a good thing to warm you and to celebrate with.
The inn was dark and smoky inside and afterward
when you went out the cold air came sharply into your lungs and numbed the edge of your nose as you inhaled. We looked back at the inn with light coming from the windows and the woodcutters" horses stamping and jerking their heads outside to keep warm. There was frost on the hairs of their muzzles and their breathing made plumes of frost in the air. Going up the road toward home the road was smooth and slippery for a while and the ice orange from the horses until the wood- hauling track turned off. Then the road was clean-packed
snow and led through the woods, and twice coming home in the evening we saw foxes. [A Farewell to Arms]
The comment by Kate Bunting
"The road was smooth... and the ice [was] orange".
is correct, the repeated "was" has been omitted here. The answer by Michael Harvey correctly identifies this as an instance of ellipsis.
One should note that the text says that the ice [was] orange "until the wood-hauling track turned off." I think it is clear that the part of the trail used for hauling wood, and thus heavily traveled on by draft horses, was turned orange from horse dung trodden into the snow and ice, while after the wood-hauling track diverged "then the road was clean-packed snow".