i only mention because this happened to a small group of wahlbergii i had a few years ago, some began to turn pink and i got quite excited as they looked really nice. they seemed normal until id check on them one day to find them lying dead on the floor, turned to gloop.
but yeh it might be due to moulting, maybe the newer skin showing through a tiny bit... or something else. its just you cna kind of tell when a mantis is about to moult in terms of its colour, some species get slightly dull/washed out in colour. ive never kept orchids before but they seem very white, and i imagine their exoskeleton is maybe more transparent than other species? im probably talking complete here, sorry, i just dont know what the problem is and putting some ideas in to the pot. i hope someone with hymenopus experience can help you. the nature of mantids growth, in terms of instars, moulting and exoskeletons leads me to think its not possible to change colour without moulting. the only thing i can imagine causing this is illness or the newer exoskeleton showing through a little more, or something along those lines as i dont think exoskeletons have these kinds of colour change properties.
(at least, not this late in an instar. of course mantids can change colour directly after a moult, as they dry off and harden, for example they can darken or change colour a little such as idolomantis adults, that from what ive seen and read, are a beige/straw colour as soon as they emerge from their exoskeleton, but after a couple of days turn gradually more green. ive never seen this first hand though).
