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