I don't agree that the blue on the image of 004 is the later dark blue, the image is also dated 87 when the unit was brand new, hence the comment about 006 in lighter blue dated 88. No way did NSE go light blue (images of 002 when new appear to be lighter blue) dark blue and back to light blue. Interestingly the image you've posted of 025 at STP does appear to be darker blue with angled upsweeps.
Your image of 004 at WFJ is a much later image (appears to have a Connex logo halfway down the first vehicle - hence no NSE logo on the front) so probably between 6 to 8 years later than the first image. Cleary has had a repaint because it does have the later curved upsweeps.
On the subject of NSE logo on the front, the grey on the model is too dark, should be lighter, but thats no biggie. Sorry if you disagree.