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