The blue collar.
After the cat was released, I was afraid that it may be captured by the MPPP workers. It seems that the MPPP workers will trap stray cats and relocate them to elsewhere if there are people who complained about the nuisance some stray cats caused. However, SPCA assured me that normally the workers won't disturb the cats that are already spayed (their ears cropped/notched). However, I was still not very comfortable with the thoughts that the MPPP workers may missed the notched ear and capture my TNR cat. So, i bought cat collar,without bell attaching(so it can hunt for food without making noises and scare away the prey) to it,for the cat. It is very tame and allowed me to wear the collar on it's neck without any resistance. This is to show the workers' that this cat 'belongs' to someone. Anyway, this cat comes back to me daily. As said by the SPCA administrator,this cat is now a happy cat, as it does not need to worry about littering problem and got bigger portion of food from me compared to other stray cats.