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