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