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