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