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)(11,17)(12,15)(13,16)(14,19)(18,23)(20,22)(21,24)(25,26)(27,37)(28,33)(29,39)(30,38)(31,36)(32,34)(35,40) involution — undirected(9,11,13,19)(10,14,16,17)(12,18,20,24)(15,21,22,23)(25,27,31,33)(26,28,36,37)(29,30,32,40)(34,38,39,35)(1,3,5,4)(2,6,7,8)(9,12,13,20)(10,15,16,22)(11,18,19,24)(14,21,17,23)(25,28,29,38,31,37,32,35)(26,33,39,30,36,27,34,40)(10,16)(14,17)(15,22)(21,23)(25,29,31,32)(26,34,36,39)(27,30,33,40)(28,38,37,35)(1,4,5,3)(2,6,7,8)(11,19)(14,17)(18,24)(21,23)(25,30,29,27,31,40,32,33)(26,35,39,28,36,38,34,37)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.