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