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