Don't worry about the colour of the stick too much. The only thing to look out for is if it turns colour at all - then you know you're in ketosis, and in the full swing of fat-burning mode.
The strength of the colour is dependent on a number of factors. As has been pointed out, if you're a bit dehydrated, there's less water in your body, so obviously the concentration of ketones in the water you expel is going to be higher. It can also be higher just after you've done exercise, because your body has been burning fat for energy.
In summary: there's not really a 'good' colour or a 'bad' colour. If it's changed colour at all, you're doing it right.
