A few more thoughts: Within their football operation, does, Linfield, for example, care one iota what University of Oregon does? Does what Oregon do affect Linfield's plans? Likely not much at all, except the idea of winning. Essentially, they are divorced from the UO in just about every way except for being in the same state.
Unless we are going to become directly affiliated with the University of Oregon (e.g. become UO-Portland), then there is absolutely no need to share anything in common with them at all. The color green, however, does link us to them. We appear as UOregon's little brother or sister sibling institution.
So why the green? Because trees are so plentiful in Portland and we are about green living? Sustainability? Would we change this aspect of our identity if our colors did not include green?
Oregon State has no green, but they are a "green university." The Blazers have no green and they are strongly identified with Portland. Therefore, I submit that the color green has really nothing manditorily to do with the identity of either Portand or Portland State and that Portland State thus need not confine itself to using it. Besides, everyone immediatly associates green with the University of Oregon. Like Linfield, let's divorce ourselves from Oregon's most decadent university, these instigators of PSU's political woes since the 1950s. What shade of green would do that for us?
I suggest we use colors that are not associated with Oregon, Oregon State and that local private school that calls itself University of Portland. If everyone gets to have white, what colors have they taken for themselves? Yellow, Orange, Green, Purple & Black.
What colors remain? There is a plethora, Guapo: {Gold, Silver, Orange-Yellow, Green-Yellow, Yellow-Orange, Yellow-Green, Bright Red, Rust Red, Light Blue, Royal Blue, Plum Violet, Gray, Charcoal Gray, Bluish Charcoal Gray, Brown, Purple-Brown (and all shades thereof)}.
Using the right shades, we could come up with a color scheme that is original, fresh and vibrant, something uniquely Portland State. Let's thoroughly divorce our identity from that of the University of Oregon.