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