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