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