When talking about which colors get which evergreen creature keywords, R&D tends to talk about a system called "primary/secondary/tertiary". In their quest to differentiate the colors in the color wheel, each should have strengths and weaknesses. Therefore, not every color gets every keyword.
Primary — This is the color (or colors) the ability is seen most in as-fan. That means it shows up in the highest volume and usually at the lowest rarity that the type of effects get used at. The primary color will almost always get this effect in a set if it's an ability we do every set. It also tends to be the color that most often pushes the power level, if it's an effect we push the power level on. There's a wide range on what primary means, because different types of effects exist at different levels. A color secondary in flying can show up way more than a color primary in taking extra turns, for instance, because there are more flying cards than extra-turn cards.
Secondary — This is the color (or colors) that an ability shows up in on a somewhat regular basis, but not as often as the primary and not always in as low of rarity as the primary. If the effect is something we do a lot of, the secondary color will usually get the ability in most sets. Sometimes a secondary color will have restrictions. For instance, red is secondary in flying, but only on Dragons and Phoenixes.
Tertiary — This is the color (or colors) that get the ability occasionally. It's not every set. For some abilities, we could go years without seeing a tertiary color using it. Tertiary colors can often come with rules, meaning it's a very narrow subset that makes use of the mechanic. For example, black is tertiary in first strike and gets it primarily on Knights, most often when paired against a mirrored white Knight.
↑Originally the creature type "Wall" carried the special rule that the creature couldn't attack. This was removed with the release of Champions of Kamigawa. Walls printed prior to that set have received errata giving them defender. Additionally, Wall of Junk, which used to be able to attack, was given defender and the Wall subtype.
↑By errata as of Ninth Edition. Originally cards that now have the subtype Aura were "local enchantments", with a type including what it could enchant, such as "enchant creature" or "enchant land".