well - it's possible
I've done it with 2 saddles, & 1 pair of riding boots
HOWEVER
forget those white or beige jodphurs! you'll need to soak them for HOURS after every ride. No matter which leather dye-setting product you use, they just don't seem to do any good.
I used leather dye on 2 saddles - and they looked nice, but the dye would rub off on everything - which made it quite a hassle. they also needed touch-ups every year. Also - the area where your stirrup leathers sit will get rubbed off REALLY quickly.
For the riding boots I just got one of those liquid sponge-applicator shoe polish things in black. It seemed to go straight over the old colour of the boots fine. You needed to re-do it before every show - but hey, need to polish boots before every show anyway.
to sum up that ramble

my 2c is don't dye saddles