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