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