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