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