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