This is from Red Bee Media who I think were responsible for the design and look of the idents
The ITV1 logo opens out at the start of each ident to encapsulate the emotion in each scene and demonstrate that ITV1 brings you all these emotions in its programming. This logo device is also taken through into the on-screen design elements for the channel in a bold and clear design that ensures that the programming shines as hero.
There's more here if you really want to read it all
http://www.redbeemedia.com/press/2006/itv.shtm l
So to answer your question I think the yellow colour represents ITV1 which starts off in a small square (the rooftop) and opens out to the wider audience ( the people ie viewers ) down below. I don't think the pattern is meant to be anything in patrticular. I guess it's all down to the individual's interpretation. Hope this answers your question.