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