Am I seeing things?
All the Zenith Z-150 boards I've ever seen had green or yellow Alps switches. That's what
DT's Zenith page says, too.
The person selling these two Z-150s on eBay says they have greens:
(1.)
Zenith Z-150 - Green Alps Vintage Keyboard ($165 OBO, free shipping)
(2.)
Zenith Z-150 - Green Alps Vintage Keyboard ($185 OBO, free shipping)
But look at these photos that accompany the listings:


Are those not
blue Alpses?
As far as I know, green Alpses are
bright green,
obvious green. Here's one in a Z-150:

...and this, as you know, are how blues look in general. They're not green. They're blue.

Maybe this seller looked up what kind of switches these boards were
supposed to have, and called them that?
Anyway, I'm just passing this your way because it was interesting... I take no responsibility for any purchasing decisions. :?)