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