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