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