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