Count rows where value differs
Try this:

Declare @T table (name varchar(10), Pattern varchar(10))
insert into @t (name, Pattern) values
('Peter', 'DRF'),
('Peter', 'DRF'),
('Peter', 'BBB'),
('Peter', 'DRF'),
('Peter', 'CCC'),
('Peter', 'CCC'),
('Sue', 'DRF'),
('Sue', 'CCC'),
('Sue', 'DRF'),
('Sue', 'VVV'),
('Sue', 'SSS')

SELECT NAME
    ,count(DISTINCT pattern) AS DistinctChanges
FROM @t
GROUP BY NAME




| name  | DistinctChanges |
|-------|----------------|
| Peter | 3              |
| Sue   | 4              |




Note: There is a difference between distinct values and the number of times a value changed assuming some kind of timeline.  

For example:
AAA, BBB, AAA, BBB, AAA, BBB, AAA would be 2 distinct changes, but 5 total times the value changed assuming some sort of order.

Which variation are you looking for?