I will explain my choice for the checkboxes colours.
First, it's in the ASP tone.
The black colour means "unchecked" and it is the same black as the edit field. The white is the same white as the font colour and notch in ASP.
The grey is logically in between. Such a tricolour can be seen in the curve level tool
As a colourblind, I have trouble to distinguish some kind of yellow-green and green-red.
I can feel some difference if the two colours are close together. But if there is just one, I have always a doubt : is that green, is that red ?
If you want coloured checkboxes, Red blue yellow is fine, but they don't match ASP's tones.
Adding symbols is also a good idea. If we can draw what we want I suggest something like :
X : nothing
- : between
√ : always (the square root is for a notch...)