Being a big fan and collector of Thousand Sons myself I love the fact that you are starting them up. However I am going to have to agree with the others here regarding the orange. It just does not look good on these models, I hate to say. The blue and the gold go together just fine and the green of the piping on the sorc is fine but that orange just does not fit, colour-wise, with the rest. It can be used in small amounts just fine but not on areas that large. Here are a few pics of a Tson terminator that I did for you to look at and see what I mean.
If you notice, there is only a couple of small spots with the orange and they are on things that are meant to stand out (eye on the knee, power cables), same with the green helmet and the red seals. The major colours are the blue and gold and that is for a reason. When you paint any model you need to choose two, not 3+, two primary colours and stick with them by making them the majority colours, in this case blue and gold. After that, choose a single contrasting colour using a colour wheel that doesn't clash with the primaries (in this case it is actually the red, there is more of it on my regular Tsons). Any other colour beyond those three should be very sparing in amount and only used to pick out objects of note like symbols, scroll cases, etc. Also, don't worry about boltgun as a colour choice as it is neutral and you will use it for things like the guns and such and it will look right on those areas.
A perfect example as well of what is making your model look 'too busy' as others have pointed out is the backpack of the champ. On that single, small bit you have 5 colours: blue, boltgun, gold, green, and orange. That is just too many colours for that and gives it a busy look. Your best bet would have been to paint the ENTIRE THING in the blue with just the pipes painted green, no other colours. That way the pack blends into the rest of the armour and further helps to tie it all together. The key thing to remember when painting minis is that less is actually more when it comes to colour and using that many colours on so many different areas of the model is distracting to the eye.