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