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