There are no rigidly defined colours for what colour striking scorpions should be.
Well, yes, their colours are green and yellow, but it doesn\'t mean you have to go with scorpion green. I think keeping a green shade would better reinforce the striking scorpion theme. Perhaps something like snot green or darker - still strong, but not as virulent.
Just as a piece of random suggestion again, especially since you seem as though you are intending this to be part of a series (even if it is only a series of 2): Have you considered making a mini to represent the pilot before their death and resurrection as a spirit stone in a wraithlord? As in, \"this was how she was 200 years ago as a striking scorpion exarch\". It might be a fun little idea to see elements (like the weaponry and/or pose) echoed between the two. I think this would be extra effective when done with each in the series.
Since this is the day for me making speculative suggestions and getting inspired myself, i rather like that idea. Similarly, before and after interrment into the sarcophagous of a dreadnought, for my purposes...
If you actually do the whole variety of aspects, i will be yet more impressed. Would be quite a sight to see them arrayed together. Admittedly the functionality of the swooping hawks and warp spiders would perhaps be unrealistic to implement, but decorative wings or extra-arm web spinners still seem fine. I\'ll leave it up to your imagination if you really reckon you could do a shining spear wraithlord though - mine doesn\'t stretch that far!
Incidentally, loving the plasticness of the wraithlord; why oh why haven\'t GW got around to plastic wraithguard yet? Here\'s hoping...