Trigrams in the sequence of hexagrams
These two simple, colour-coded images are intended to make it easier for people to look at the patterns and assymetries of the arrangement of trigrams in the King Wen sequence of the hexagrams - the traditional sequence, that is. They are arranged by 'decades' of hexagrams, as this seems to me to bring out the greatest latent significance; it also respects the division into Upper and Lower Canons.
This first image has one colour per trigram. (Thanks to LiSe Heyboer for the colour scheme!)
The second image simplifies matters by showing the symmetrical pairs (the ones that are generated by inversion) as a single gua, and representing the inverted pairs of trigrams - sun and dui, gen and zhen - in the same colour.
Further reading
There's an excellent article by Danny Van den Berghe on the I Ching Landscape (direct pdf link - right-click to download) which is the best discussion I've seen of trigrams in the hexagram Sequence. And more good reading on his articles page.
You might also enjoy contemplating the sequence of hexagrams in Steve Marshall's representation of its yin and yang lines.