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