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