This is a Deceptive Sallow Moth (Feralia deceptiva).
This species is an early spring flier, on the wing from late February through May according to The Moths of Western North America (Powell and Opler 2009).
The caterpillars of this species are also green and white. They feed on the young foliage of Douglas-firs.
Deceptive Sallow Moths occur from British Columbia to central California. They're often attracted to lights at night, so keep an eye out for them if Douglas-firs are nearby.
P.S. Although it's a wee bit late, this moth seems an appropriate way to wish everyone a Happy St. Patrick's Day!