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