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