must discolour
Regular verb: discolour - discoloured- discoloured

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must discolour
you must discolour
he must discolour
we must discolour
you must discolour
they must discolour 	I must be discolouring
you must be discolouring
he must be discolouring
we must be discolouring
you must be discolouring
they must be discolouring	I must have discoloured
you must have discoloured
he must have discoloured
we must have discoloured
you must have discoloured
they must have discoloured	I must have been discolouring
you must have been discolouring
he must have been discolouring
we must have been discolouring
you must have been discolouring
they must have been discolouring	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't discolour
you mustn't discolour
he mustn't discolour
we mustn't discolour
you mustn't discolour
they mustn't discolour 	I mustn't be discolouring
you mustn't be discolouring
he mustn't be discolouring
we mustn't be discolouring
you mustn't be discolouring
they mustn't be discolouring	I mustn't have discoloured
you mustn't have discoloured
he mustn't have discoloured
we mustn't have discoloured
you mustn't have discoloured
they mustn't have discoloured	I mustn't have been discolouring
you mustn't have been discolouring
he mustn't have been discolouring
we mustn't have been discolouring
you mustn't have been discolouring
they mustn't have been discolouring	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I discolour?
must you discolour?
must he discolour?
must we discolour?
must you discolour?
must they discolour? 	must I be discolouring?
must you be discolouring?
must he be discolouring?
must we be discolouring?
must you be discolouring?
must they be discolouring? 	must I have discoloured?
must you have discoloured?
must he have discoloured?
must we have discoloured?
must you have discoloured?
must they have discoloured? 	must I have been discolouring?
must you have been discolouring?
must he have been discolouring?
must we have been discolouring?
must you have been discolouring?
must they have been discolouring? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I discolour?
mustn't you discolour?
mustn't he discolour?
mustn't we discolour?
mustn't you discolour?
mustn't they discolour? 	mustn't I be discolouring?
mustn't you be discolouring?
mustn't he be discolouring?
mustn't we be discolouring?
mustn't you be discolouring?
mustn't they be discolouring? 	mustn't I have discoloured?
mustn't you have discoloured?
mustn't he have discoloured?
mustn't we have discoloured?
mustn't you have discoloured?
mustn't they have discoloured? 	mustn't I have been discolouring?
mustn't you have been discolouring?
mustn't he have been discolouring?
mustn't we have been discolouring?
mustn't you have been discolouring?
mustn't they have been discolouring?