So, after wanting to end my life after my berries not taking any effect, I decided to try out the 6 hour window and see what I could do.

I fed an initial 3 berries and waited 3 hours (I took a nap) and now I fed him 27 more berries and 10 pears to get Orthard Blue (fingers crossed).

If the color is correct after this, that means that you can effectively add more fruit any time in the 6 hours window and still get the intended result, however, I failed to try and alter the ordering of the final fruit to see if it had any effect.