Hi Breis,
If you're insistent on color and text-to-speech, it looks like the iPad is what you'll want. It is expensive, though, and I know you mentioned caring about cost. Something will have to give in your constraints, as their intersection currently yields an empty set.
Explore your options:
text-to-speech (TTS) ereaders
color ereaders
low-cost ereaders
At the site behind those links, you can add or subtract preferences on
factors until you narrow in on the best fit for you.