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