Hello again and thanks for waiting.
Sorry to hear about Max's problem. Head tremors are very unlikely to be associated with changes in eye colour. Ear infections can be very itchy indeed so this is the most likely cause but if the tremors continue once the ear infection is resolved then further diagnosis is needed.
I have worked out an answer for you, please read it through and see what you think ...
1. Sometimes just cleaning the ears alone is not enough, if there is an active infection of some sort then the brown discharge will just come back.
2. In this age group ear mites are very common and easy to treat but the first thing to do is to make sure of the diagnosis. If you gently to a sample of the brown stuff in your cat's ears with a cotton bud and looked at it carefully with any lens you have you might be able to see the ear mites as small white dots moving about. That would clinch the diagnosis.
If this is the case then the over the counter ear mite drops from your vet or pet stores etc. are very effective as all they contain are insecticides, they actually work well. But you would give them for five days, wait five days and then dose again for a further five days to catch any newly hatched mites.
3. If you do not see ear mites on the cotton bud then there are a number of other possible causes of ear infections including fungal infection and bacterial infection. If this is the case you would be better to see your vet again as products which contain prescription drugs such as antibiotics will be the best.
4. You can reference this web site for further information on the topic : LINK
I hope I have covered your question fully enough but if you would like further clarification or to talk things over a bit more then I will be on-line for the next hour or so and I will be more than pleased to continue working with you.