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