Look at this orb:
and this one (note: NOT my picture, just googled poison wind globadier)
You've got the darkest colour at the very 'bottom' (as far as an orb has one of those), most of the orb is different mid-tones finishing off with the brightest colour in a similarly small amount as the darkest.
Blending from your base colour to a much brighter/paler blue on the top part of the orb would be the best way of doing it. Alternatively some very gradual layering would work.similarly. wash it blue afterwards to tie things together better and you're sorted. A dead easy way of getting your different blues is to add a very pale grey (vallejo ghosty grey for example) to the base colour.
With your model I would leave the bits closest to the staff the darkest.