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