Have you seen any of them moving at all? And do you see this stuff around/in his enclosure, or just on his body? Any itching or rubbing of his body on the tank or decor? Any other weird or abnormal behaviour from him? Appetite? Activity level? And when is the last time he shed?
In the first photo it looks like it could possibly be mites to me, actually that first photo with the bright-red stuff on his head looks just like a certain type of mite. But in the lower photos it doesn't look the same, could just be the lighting...
Do you have a magnifying glass by chance? If so, those would be a type of mite that you could see individually under a magnifying glass, look for legs...If the infestation gets bad enough they can end up looking like red paint or a stain of some sort, if you've ever seen them outside on a plat leaf it's very much the same. Birds get these as well often...
However, it's quite possible it's a stain of some type of you haven't tried to
bath him with a toothbrush..Have you? If not, I'd try a regular, warmer than normal
bath (no Betadine in it) and after you let him soak for 5 minutes in the water, use a soft toothbrush and try to brush some of it off. If it won't come off at all, then it's most likely not a "mite", but it could still be a fungal or bacterial infection of his scales.
Turtles/tortoises get a similar looking fungal infection of their shells and their scales on their legs, it can be detrimental to their shells (different than a lizard's skin/scales so don't worry to much) because it basically "rots" their shells away. I have seen this a few times on the shells of turtles/tortoises at the Reptile Rescue I work at.
How long has he had this? And did it start in one spot (like on his head) and then spread to other parts of his body, or did it all appear at one time?
I'm going to assume it's not just "staining" from fruit or other food sources, as you said you've given Betadine baths, which would was that off.
I'm going to look in my texts, but my best guess is that unless it brushes off with a toothbrush in a warm
bath (you can even try just a dab of plain old Blue Dawn Dishwashing liquid on the brush, this is safe for him and may help if it is a tough stain), you need to take him to an experienced reptile vet ASAP to get it examined and have them do a "Skin Scraping Test" that they will have to send off to be analyzed at a lab. This will diagnose and/or rule-out a bacterial or fungal infection, and a parasitic infection with mites or other insects/arthropods, etc.
DO NOT APPLY ANY MORE OVER-THE-COUNTER MITE SPRAYS, POWDERS, CREAMS, ETC.!!!! This can actually make it worse, depending on what it is, or could poison him as well. I never, ever, ever use any over-the-counter mite, flea, tick, insect, etc. sprays, powders, creams, lotions, spot treatments, etc., not on my dragons, birds, or dogs! Ever! So many dogs, cats, birds, rodents, reptiles, etc. have been killed or had to be euthanized due to over-the-counter "bug remedies" made by companies such as Hartz, Sargent's, Pet Armor, Flukers, Ecotrition, Kaytee, etc. that I just don't trust them, plus they usually don't work anyway. You're much better off using holistic and natural solutions. I use clove oil on my dogs as a flea/tick spot remedy monthly and a few drops in their monthly
bath shampoo, and neither have ever had a flea or tick even though I live in the middle of farmland and forest.