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