Hello...
That may be a sign of chronic sinusitis are there any associated symptoms like facial pressure or pain, if yes , then this often requires a different, more specialized treatment approach.
The discoloration could be due to a chronic, non-infectious inflammatory issue that the antibiotics would not address.
like Severe ongoing allergies (allergic rhinitis), or structural issues in the nose like nasal polyps or a deviated septum, any long standing forigen body, this can lead to persistent inflammation, congestion, and colored, stagnant mucus[occasionally foul smelling].
Next Steps
1. do u feel any facial pain/heaviness?
2. is there any foul smell?
3. breathing difficult?
4. disturbed sleep?
if yes then u should immediately consult an ENT , you may need a CT scan of your PNS or an nasal endoscopy.
Health Tips
identify any triggering factors wich worsens your condition.
plane steam inhalation may be of help to you.