In Classical Gluonic there are two completely separate existential/copular verbs, a positive one and a negative one, and these are also used as coverbs. The negative copula is the primary means of verbal negation.

Existence/Copula

The verb "aa" is the positive existential verb. Its base meaning is something like "there is." It is obligatorily patientive intransitive. Example, again assuming that the referent has already been introduced:

Aalo tuulao.
be-PAT.BLUE house.BLUE-SG.ABS.BLUE

"There is a house."

To make it into a copula, add the predicate as an applicative. The predicate can be any noun-like object that is able to have colour. Example with an adjective predicate:

Tuulao aalomu ivoono.
house.BLUE-SG.ABS.BLUE be-PAT-BLUE-APL.BLUE white.BLUE-SG.ABS.BLUE

With an adjective predicate, the predicate must agree with the subject in colour, and in order to avoid ambiguity between whether you are talking about a "white house" or a "house that is white," the subject is sometimes fronted.  When the predicate is a noun or more noun-like word, the subject is much less likely to be fronted and colour agreement is not needed:

Aalome rro veppehe.
be-PAT.BLUE-APL.RED 3.SG.INAN.BLUE ball.RED-SG.ABS.RED

"It is a ball."

"Aa" glosses as "be" in its existential or copular sense.

If the subject and predicate don't agree in colour, however, as they often don't, the speaker might use a strong colour clitic on the predicate to change its colour to match the subject. This is a touchy thing to do from a pragmatic perspective, if everyone in the conversation does not agree with the identity being expressed, however, because doing so forces everyone to implicitly accept it, or else to speak while disagreeing on the colour of referents. Conversely, failing to change the colour of the predicate might communicate hesitance on the part of the speaker about the conclusion.

Non-Existence/Negative Copula

The verb "ki" is the negative existential verb. Its base meaning is something like "there isn't." It is obligatorily patientive intransitive. Example, again assuming that the referent has already been introduced:

Kilo tuulao.
be.NEG-PAT.BLUE house.BLUE-SG.ABS.BLUE

"There isn't a house."

To make it into a copula, add the predicate as an applicative. There is a shift in meaning - where without the applicative it asserts that its subject doesn't exist, with the applicative it asserts that its subject does exist, but doesn't have the stated quality, i.e., does not exist with that quality. The predicate can be any noun-like object that is able to have colour. Example with an adjective predicate:

Tuulao kilomu ivoono.
house.BLUE-SG.ABS.BLUE be.NEG-PAT-BLUE-APL.BLUE white.BLUE-SG.ABS.BLUE

With an adjective predicate, the predicate must agree with the subject in colour, and in order to avoid ambiguity between whether you are talking about a "white house that doesn't exist" or a "house that isn't white," the subject is sometimes fronted.  When the predicate is a noun or more noun-like word, the subject is much less likely to be fronted and colour agreement is not needed:

Kilome rro veppehe.
be-PAT.BLUE-APL.RED 3.SG.INAN.BLUE ball.RED-SG.ABS.RED

"Ki" glosses as "be.NEG" in its existential or copular sense.

Classical Gluonic is not a negative concord language - a double negative is a positive. The negation clitic -K*I ('kki) is used to negate noun phrases.

Existential Verbs as Coverbs

Both "aa" and "ki" can be coverbs. "Aa" serves as a "fortitive." It just emphasizes or strengthens the meaning of its infinitive object. This is mainly for rhetorical impact and is less used than the negative version. The negative coverb "ki" is the only mechanism for verbal negation in Classical Gluonic.It behaves exactly like any other coverb, including chaining, and it applies to the verb or coverb directly in front of it. Example:

Kilo meeta gorano.
NEG-PAT.BLUE sleep child-SG.ABS.BLUE

"The child isn't sleeping."

The fortitive version is:

Aalo meeta gorano.
FORT-PAT.BLUE sleep child-SG.ABS.BLUE

This means, "The child does sleep." It's just a more emphatic way of saying the same thing without the coverb.

As coverbs, "aa" glosses to FORT and "ki" glosses to "NEG."