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