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