What is the indicator for honey?

I'm not sure what you mean by 'indicator', but if you mean how do we know when the honey is ready for collection, then we wait for the bees to let us know. They will cover the honey cells with wax when they think it is ready. They may leave a few cells open, either because the bees think they are not full enough or because they are feeding from them, so we wait for most of the comb to be covered.