I didn't want to change the factory deco too much, because I think they did a pretty alright job with the figure to begin with, but there were a few things I figured I'd add to it.
Vehicle mode:

As you can see, the trim at the bottom has been coloured silver, the lights have been done in a light metallic blue, and the rest of the door has been coloured in (though in photographs the colour doesn't match up as well)

Here we see that the rest of the lights have been given the metallic blue treatment as well

With the light shining through, the effect is less noticable... but the Autobot logo is now silver on red, instead of straight red.

Notable on top, the lights are now metallic blue surrounded by silver.
onto the Robot mode:

Here we see where I really started to fix things up, mostly unseen due to the lighting is the gold rings on the midsection, just above his legs. Also the blue strips underneath his truck parts on his chest.

The feet, here I've added the blue strip missing from the figure, and changed that unsightly red piece to silver.
Also changed is the part hanging down from the leg armour, which is now red.

His chest (in "I am Optimus Prime" position) reveals the detailing done on the Autobot symbol here, and the copper centerpiece has been changed to gold. Also detailed the rods for the windshield wipers for no apparent reason.

Added the blue parts on the silver shoulder strut things, and now onto where this really shines for me, The Head!


Lots of small details done here: Silver added to a lot of sections on the head where it was missing, as well as a few gold bits here and there really serve to bring out more detail in the sculpt that was kinda washed out by the straight blue it originally was.
I took a picture of the back of the head, which is strangely absent from my computer... I had added some silver to a couple areas and painted the vents gold... ah well.
Since snapping these pictures I've also added the silver to his swords.
So, for not really wanting to change the factory deco too much, I think it turned out pretty good, anybody else got a say? Comments? Criticism? If so, post 'em here!
- Sam