That looks nice.

I feel like a designer needs to first articulate the intent of the colour usage, before deciding on it.
Because in some places, you want a higher contrast, while in others, you just want a separate colour, without stuff popping out too much. Then there is also the case of less contrasting colours popping out more, because they were used in a larger area than they were chosen for and same the other way round, when you choose a lower contrasting colour combination due to the both colour areas being large enough, like window background vs document background, but then if you end up using the combination for something like text, it becomes hard to read.

So for instance, using the "Tower of Glass" example, one can use the last 2 colour for things like:

• window background vs button/field background
• button normal vs button hover
• background vs alt background (though in this case, I would be looking for even lower contrasting colours

... but not for cases like:

• background vs text
• background vs border

While you could still also use it for text vs alt-text.