Hello,
It might be because of the holi colour which may go inside the ear canal and mixed with the wax while having a bath or cleaning.
No need to worry so much unless or until it's green colour discharge which suggests us of infection.
Next Steps
Clean your ears on a regular basis, in case of any doubt please consult a nearby Ent Doctor.
Health Tips
Avoid excessive use of ear buds to clean the canal.
Do not use any pointed object to clear the ear canal.