Is it obligatory to continue spreading goodness and knowledge among colleagues despite the rejection and lack of response encountered, and what actions would increase their receptiveness?

The caller to Allah and teacher of good to people should be characterized by patience, gentleness, and wisdom. If some colleagues desire to learn and others refuse, let him continue to offer his lessons to those who wish to learn. If he encounters envy or jealousy, he must be patient, overlook their ignorance, and respond to their ill-treatment with kindness, as Allah Almighty says: (And the servants of the Most Merciful are those who walk upon the earth easily, and when the ignorant address them [harshly], they say [only], "Peace.") Al-Furqan/63.

However, if they all refuse the lessons, wisdom dictates not to compel them, as Allah Almighty says: (Invite to the way of your Lord with wisdom and good instruction, and argue with them in a way that is best. Indeed, your Lord is most knowing of who has strayed from His way, and He is most knowing of who is [rightly] guided.) An-Nahl/125.

Wisdom means putting things in their proper place and choosing the right time and person for admonition. If colleagues are unwilling to learn, then seek others who are eager to benefit.