One way is to get all the IDs that have ColorID = 2 and join to that in update:
with cte as
(
select distinct id from tblPage where colorid = 2
)
update tbl
set imagetype = CASE WHEN cte.id IS NOT NULL THEN 'TIFF-JPEG' ELSE 'TIFF' END
from tblPage tbl
left join cte on cte.id = tbl.id
Alternatively you can group by ID and look for max ColorID:
with cte as
(
select id, max(colorid) as maxcolorid
from tblPage
group by id
)
update tbl
set imagetype = CASE cte.maxcolorid WHEN 2 THEN 'TIFF-JPEG' ELSE 'TIFF' END
from tblPage tbl
inner join cte on cte.id = tbl.id