Is secretly taking a remaining quantity of coffee, after it was served to colleagues and then disputes arose with them, considered theft, given that the intention was to retrieve what was brought?

As long as you brought the coffee, taking what remains of it is not considered theft. It can be considered a breach of murūʾah (chivalry/courtesy), as bringing it and making it available for use in the company implies a permission for colleagues to benefit from it, not an act of transferring ownership to anyone. Ibāḥah (permission to use) differs from hibah (gift) and ṣadaqah (charity) in that the latter two involve transfer of ownership.