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