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