could yellow
Regular verb: yellow - yellowed- yellowed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could yellow
you could yellow
she could yellow
we could yellow
you could yellow
they could yellow 	I could be yellowing
you could be yellowing
she could be yellowing
we could be yellowing
you could be yellowing
they could be yellowing	I could have yellowed
you could have yellowed
she 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
she 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 	Perfect 	V-ing perfect 	
I couldn't yellow
you couldn't yellow
she couldn't yellow
we couldn't yellow
you couldn't yellow
they couldn't yellow 	I couldn't be yellowing
you couldn't be yellowing
she couldn't be yellowing
we couldn't be yellowing
you couldn't be yellowing
they couldn't be yellowing	I couldn't have yellowed
you couldn't have yellowed
she couldn't have yellowed
we couldn't have yellowed
you couldn't have yellowed
they couldn't have yellowed	I couldn't have been yellowing
you couldn't have been yellowing
she couldn't have been yellowing
we couldn't have been yellowing
you couldn't have been yellowing
they couldn't have been yellowing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I yellow?
could you yellow?
could she yellow?
could we yellow?
could you yellow?
could they yellow? 	could I be yellowing?
could you be yellowing?
could she be yellowing?
could we be yellowing?
could you be yellowing?
could they be yellowing? 	could I have yellowed?
could you have yellowed?
could she 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 she 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 	Perfect 	V-ing perfect 	
couldn't I yellow?
couldn't you yellow?
couldn't she yellow?
couldn't we yellow?
couldn't you yellow?
couldn't they yellow? 	couldn't I be yellowing?
couldn't you be yellowing?
couldn't she be yellowing?
couldn't we be yellowing?
couldn't you be yellowing?
couldn't they be yellowing? 	couldn't I have yellowed?
couldn't you have yellowed?
couldn't she have yellowed?
couldn't we have yellowed?
couldn't you have yellowed?
couldn't they have yellowed? 	couldn't I have been yellowing?
couldn't you have been yellowing?
couldn't she have been yellowing?
couldn't we have been yellowing?
couldn't you have been yellowing?
couldn't they have been yellowing?