English verb conjugation
COULD YELLOW

Regular verb: yellow - yellowed - yellowed

Affirmation

Simple form	V-ing form
I could yellow you could yellow he could yellow we could yellow you could yellow they could yellow	I could be yellowing you could be yellowing he could be yellowing we could be yellowing you could be yellowing they could be yellowing
Perfect	V-ing perfect
I could have yellowed you could have yellowed he could have yellowed we could have yellowed you could have yellowed they could have yellowed	I could have been yellowing you could have been yellowing he could have been yellowing we could have been yellowing you could have been yellowing they could have been yellowing

Negation

Simple form	V-ing form
I could not yellow you could not yellow he could not yellow we could not yellow you could not yellow they could not yellow	I could not be yellowing you could not be yellowing he could not be yellowing we could not be yellowing you could not be yellowing they could not be yellowing
Perfect	V-ing perfect
I could not have yellowed you could not have yellowed he could not have yellowed we could not have yellowed you could not have yellowed they could not have yellowed	I could not have been yellowing you could not have been yellowing he could not have been yellowing we could not have been yellowing you could not have been yellowing they could not have been yellowing

Interrogative form

Simple form	V-ing form
could I yellow? could you yellow? could he yellow? could we yellow? could you yellow? could they yellow?	could I be yellowing? could you be yellowing? could he be yellowing? could we be yellowing? could you be yellowing? could they be yellowing?
Perfect	V-ing perfect
could I have yellowed? could you have yellowed? could he have yellowed? could we have yellowed? could you have yellowed? could they have yellowed?	could I have been yellowing? could you have been yellowing? could he have been yellowing? could we have been yellowing? could you have been yellowing? could they have been yellowing?

Interro-negative form

Simple form	V-ing form
could I not yellow? could you not yellow? could he not yellow? could we not yellow? could you not yellow? could they not yellow?	could I not be yellowing? could you not be yellowing? could he not be yellowing? could we not be yellowing? could you not be yellowing? could they not be yellowing?
Perfect	V-ing perfect
could I not have yellowed? could you not have yellowed? could he not have yellowed? could we not have yellowed? could you not have yellowed? could they not have yellowed?	could I not have been yellowing? could you not have been yellowing? could he not have been yellowing? could we not have been yellowing? could you not have been yellowing? could they not have been yellowing?