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