I wrote copious notes in my book on how these exercises made me focus on the quality of colours and their impact on the adjacent or surrounding colours. To summarise, I found the red centre tended to dominate over other colours, except with the yellow, where they challenge for supremacy. It adds heat and warmth to the other colours. On pink, it pulls the eye towards it, and tends to extract the colour from the pink, to me.
Green is less strong, and tends to diminish in blue tones. It is bold against red, is swallowed up by yellow and is an uncomfortable mix with pink in these shades of paper colours. Yellow centre is strong and domineering, I noted that it seems to add purity to each colour. Blue is always bolder than the secondary colours, but is softer than yellow and red. It is more calming in effect and relaxes the eye.`