Most of the examples that you show are ugly, and only serve to illustrate the excessive use of colour that distracts from the message conveyed by the text.
For example: Look at the headings Contents, Preface, and Introduction in your book. They should be a single colour. The three-coloured drop capitals are fine, but three-coloured headings are just gaudy. I would not even want to read the book if it was laid out like that.
Effective use of colour may well help to communicate a message, but mixing three colours in a single glyph is just distracting. It might work in a logo, but not in text that needs to be read and understood.
This is more than enough colour to make the word stand out: