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