Good work on the site.
You've integrated the red, green, yellow, blue colours well across the site like down the sidebar, I feel that works well.
The only thing that bothers me is that it feels quite spaced out especially between the text lines. The sidebar is good with little spacing between lines but on the homepage it feels too stretched like it's trying to cover the height of all three images within the content area.
If you're trying to make everything fit it looks like it's not going so well with the sidebar being longer than the pictures which is longer than the introduction text. Perhaps rearranging some elements on the front page would make everything fit in well instead of having an obvious 'side bar' and aligning the images to the right of the main content area.
Also the front page slider might work better if each of the coloured blocks on the top left hand corner allowed you to switch between slides as there's no control over them at the moment.
lastly you might want to link some of the top level menu items. I was wondering why they didn't work until the drop down loaded but for people who don't understand or haven't had it load quick enough it might benifit to either link the top level to the first page on the drop down (Eg, link the 'About' menu link to 'The Company' page) or even add in a little arrow indicating something should appear underneath.
Hope this helps.
Keep up the good work.