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