One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,5)(4,6)(7,8)(9,10)(11,19,21,31)(12,16)(13,17)(14,18)(15,22,27,25)(20,33,34,40)(23,29)(24,30)(26,32)(28,35,38,37)(36,39)(1,3,4,7)(2,5,6,8)(12,23)(15,27)(16,29)(19,31)(20,34)(24,36)(30,39)(35,37)(9,11)(10,15)(12,20)(13,25)(14,21)(16,28)(17,31)(18,27)(19,32)(22,26)(23,34)(24,37)(29,38)(30,40)(33,39)(35,36) involution — undirected(2,6)(5,8)(9,12,13,24,14,23,26,36)(10,16,17,30,18,29,32,39)(11,20,25,37,21,34,22,35)(15,28,31,40,27,38,19,33)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.