Dont count on it. Theres three main reasons why they made it always red. The most important being visibility. Not for the passenger, who can just simply read the letter/number, but for other train crews. Its more of a quicker response to see a red light and respond by reflex that there is a train in front of you than to figure out another color. This was how this was explained to me by engineers when the 142's were being designed. We as railfans may want the return of colored bullets, but the focus is on operations. Then there's cost. A multicolored LED costs more than a red one. And not too long ago, certain colors on LEDs werent possible. They are now, but at a slightly higher cost. Especially when you take the cost of one single LED, mutiply that by the number of LEDs in each end route sign, then multiplying that by the number of "A" cars ordered. Then its spare bulb factor.
And in all honestly, its only difficult to tell what train it is if you cant read a single letter or number. Then theres the side signs that you can read.......