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