A. Would you like to try some pants.
B. I want to try those blue pairs.
Is it acceptable to replace "pairs" by "ones"? Please.
Yes. But, it's "the blue ones" or "the blue pair." Assuming you are talking about one pair of pants.
I want to try those blue ones - the blue pants, the blue pair of pants..
Is it right to replace "those blue ones" by "that blue ones" ? Please.