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