Lascaux: The Axial Gallery: Red Shift
The three horses nearest to the sign by the falling cow are shown in perspective. Each horse is a different shade of red. They may depict red shift, whereby for an observer, an object becomes dimmer and redder as it is pulled into a black hole.
Reference
Image Credit:
Chevaux entre la Vache qui tombe et les bouquetins affrontés. Paroi Droite. Diverticule Axial: Norbert Aujoulat © MCC-CNP, 2004: Lascaux, le geste, l’espace et le temps, Paris, Le Seuil: Lascaux: Visite de la Grotte: Ministry of Culture, France: http://www.lascaux.culture.fr/#/fr/mediatheque.xml/40