How to construct potential form for adjectives

Question

I could not help but notice that adjectives cannot directly conjugate to have a potential form:

E.g. 赤い does not become 赤られる for (can be red)

(Question) Which of the below are acceptable forms to convey a potential for adjectives? What about な-adjectives?:

• 赤く出来る (using potential-form of する)

• 赤くなれる (using potential-form of なる) (This seems to mean "can become red" which is so very different from "can be red")

• EDIT: 赤いがなり得る (I found this construction, I'm not sure what it does and how different it is from 赤くなれる and 赤くなり得る)

• 赤いことができる　(Using the sentence pattern ～ことができる)

I also thought about using the copula but there isn't any potential form for だ/です. Unless it's であられる?

• Would 赤いであられる make sense for "can be red" ?

Answer 1

It depends on what you mean by “potential form.”

Both れる/られる and ことができる are attached to a verb and their basic meaning is “have the ability to do.” (れる/られる has very different meanings such as passive and respect, but I ignore them for the purpose of this answer.) Because they are about the ability, the subject is usually animate.

The combination of ある+られる would be あられる, but this combination is ungrammatical for a reason I do not know.

Although the meaning of れる/られる/ことができる has large overlap with the meaning of “can” in English, it does not cover the usage of “can” in “can be red” (= may be red; possibly be red).

“Possibly” can be translated as “～可能性がある” as cypher wrote in a comment, or “～かもしれない.” Therefore, “can be red” is 赤い可能性がある or 赤いかもしれない. Although 可能性がある and かもしれない are not completely the same, I am not prepared to explain the difference now.

Below I will try to explain whether each of your examples is grammatical or not and what its meaning is.

• 赤くする is “redden (something),” and 赤くできる (or 赤く出来る, although できる in this usage is usually written in hiragana) is “have the ability of redden (something).”
• 赤くなれる is “have the ability to turn red,” but I do not know when it can be used.
• 赤くなりうる is “possibly turn red.” Unlike 可能性がある and かもしれない, [得]{う}る in this meaning can be only attached to a verb.
• 赤いがなり得る is ungrammatical because 赤いがなる is ungrammatical.
• 赤いことができる is ungrammatical because ことができる can be only attached to a verb as I wrote above.
• 赤いであられる is ungrammatical for two reasons: 赤いである is ungrammatical, and the combination あられる is somehow ungrammatical as I wrote above.