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