One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,5,6)(3,7,4,8)(9,10,13,15)(11,19,22,31)(12,23,24,39)(14,27,26,18)(16,30,28,20)(17,33,29,25)(21,36,38,32)(34,37,40,35)(2,6)(7,8)(10,15)(11,20)(12,24)(14,26)(16,31)(17,29)(19,28)(21,37)(22,30)(32,40)(34,36)(35,38) involution — undirected(1,3,5,4)(2,7,6,8)(9,11,14,20,13,22,26,30)(10,16,18,19,15,28,27,31)(12,21,25,35,24,38,33,37)(17,32,23,34,29,36,39,40)(9,12,14,25,13,24,26,33)(10,17,18,23,15,29,27,39)(11,21,20,35,22,38,30,37)(16,32,19,34,28,36,31,40)(1,4,5,3)(2,7,6,8)(10,15)(16,28)(17,29)(18,27)(19,31)(23,39)(32,36)(34,40)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.