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