The color change is definitely a shed coming on, and that can take a while to actually start happening. The skin on top has to loosen and dry up, and more importantly the new skin underneath has to be ready to be exposed. It will happen, don't worry, it does take some time occasionally, especially on their tails, but it's completely normal.
As far as the "dents" in his tail, they are just damaged scales, probably from a prior injury like a sibling biting him, or someone shutting his tail in an enclosure door. Either way, they don't appear as if they are open wounds, it looks as though they healed completely, which is what is important. As long as you don't see any open wounds or sores, and it's just the "dents", then it's fine. His tail with most likely look like that forever, sheds may help the scales even out a bit over time, but as long as they do not open up he's fine.
The color change is definitely a shed coming on, and that can take a while to actually start happening. The skin on top has to loosen and dry up, and more importantly the new skin underneath has to be ready to be exposed. It will happen, don't worry, it does take some time occasionally, especially on their tails, but it's completely normal.
As far as the "dents" in his tail, they are just damaged scales, probably from a prior injury like a sibling biting him, or someone shutting his tail in an enclosure door. Either way, they don't appear as if they are open wounds, it looks as though they healed completely, which is what is important. As long as you don't see any open wounds or sores, and it's just the "dents", then it's fine. His tail with most likely look like that forever, sheds may help the scales even out a bit over time, but as long as they do not open up he's fine.