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