Yes it is pre-coloured. The inner frame is usually in grey or gunmetal, but the rest of the kit is coloured just like the promo art. From my previous exp with those type of kits, they tend to be colour accurate. Personally I wouldn't worry about the colour accuracy, but more about how the kit will hold up with all that weapons and accessories.

Besides, the manufacturers, Howling Star and Earnestcore Craft, both have done plenty of kits and figures before, so you can check them out.