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