I've just started using After Effects and I have to say it's a very steep learning curve and really time consuming!
I hope this makes sense to some of the more seasoned users.
You could probably do it in one bold sweep by using a single text layer with text animators for color and opacity. Otherwise pre-composing might be advisable, though it realyl depends on how you have laid out the text. In the end it may be simpler to deal with multiple layers. As such, for the life of it don't use "dumb" effects like Change To Color. Instead crossfade between two versions of the same text or use more controllable color effects like Hue/ Saturation or Tint and animate their internal strength& opacity.