All your colors are belong to us, part III

About a year ago I noted that universities were claiming to "own" certain color combinations and seeking to prohibit non-licenced retailers from producing clothing or other products in those colors.

Now it seems that Scotts Miracle-Gro Inc., a $2.2 billion giant that dominates its market, has asserted ownership of the colors green and yellow. They're suing Terracycle, a relatively miniscule producer of organic fertilizer derived from earthworm excrement. The suit also seeks to prohibit TerraCycle from stating that its products are superior to "leading synthetic fertilizers" in various ways.

Is this a developing legal trend, or are corporate claims to "own" colors, per se, an established part of the legal world?