Why So Few Green-Colored Butterflies in North America?

In a crude search of the Kaufman Field Guide to Butterflies of North America, I found only 18 species with green or 2.4% of all species. Green-colored butterflies are predominantly Hairstreaks, why is that? Below is a stunning Juniper Hairstreak (Callophrys gryneus) that I recently photographed (lifer). I did a Google Scholar search of the lepidopteria literature and could not find an answer to my question. Did come across Elements of Butterfly Wing Pattern by H.F. Hijhout which detailed that butterfly spots, stripes do not vary in positions across individuals, quite different than human fingerprints or zebra stripes and leopard spots. Hijhout states that butterfly spots/stripes are an "individuated"character that can be given a name and traced over the phylogenetic tree.

Juniper Hairstreak

Here's a couple of photos of the red/orange butterflies (can you identify to species?) coming to Sawmill creek (Sapphire Mountains of Stevensville, MT) to "mud"... find something great in your own neighborhood!