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