Use constants for ST_PresetColorVal values

Again no need to adapt dmapper/rtftok for these, see commit
020f46d17065b8b00365eab7a809ce980ebfb59a (Use constants for ST_Em
values, 2014-10-07).

Change-Id: Ie67f7a4d251525b5f8799cf613bea56ad82f7a57