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