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