When trapping a tinted color, what's the right move trap it with the same percentage of the tint or the 100% of it ? (in flexography or screen printing to be specific)
The trap (or grip as some people like to call it) should be a continuation of the shape that you are trapping, so the overlapping area should always be the same colour and tint as the rest of the shape.
To put to another way; If you were to take away the object that your shape is trapping to, then it should just look like a slightly larger / expanded version of the original (untrapped) shape so you wouldn't expect to see any distinct key line or area of different colour.
Hope that's clear and helpful.