I am not sure about the material rules behind accent colours but as a digital designer I prefer to subscribe to a mix of brand, aesthetics and colour theory.
I start with the clients brand colours and work out how they appear on screen. Look at contrasts and complimentaries. Each have their place in the usability. I create a colour page for the clients to talk them through how the brand colours work and always link this back to UX. If they are lacking in a colour for particular puprsoses e.g. a contrasting colour, then I talk them into adding another colour to their brand palette.
The next step is to take into consideration users physical eyesight.
If you are following accessibility guidelines then I wouldn't be using blue on blue. It doesn't have a high enough contrast for protanopia and deuteranopia colour blindness.
And for accessibility guidelines, these are issued by Governments. And published online. Here's an example of the Australian guidelines https://www.w3.org/TR/WCAG20/