- Location
- Earth
Or it could be seen as adding another layer of depth to the writting the same way the more established italic or capital letters do. The proper rules of writting evolve over time sometimes because we discover improvements (space between words makes the reading easier and faster, a single sense of lecture: from left to right is more efficient than changing after every line etc.) and sometimes because we have access to new tools that made innovations impractical. Colour coding is something that was unpractical before because of the rarity of coloured ink and because it takes longer to write. With the advent of computer, such colour coding becomes possible and could theoretically become part of legitimate established writting practice; although I will admit I do not see this coming because it still takes longer and the mechanics of acquiring legitimacy makes it difficult in our society because of it's origins.It is cheating... and frankly kind of derivative. You don't need to color code text to communicate what emotions a character is feeling. We ought to be able to tell that from the writing. I would knock it out, if you're asking for opinions. You don't need that crutch.
In short ? Go for it if you feel like it adds something to the story you are writting.