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