What is the study with the dual-task experiment that involved a colour-wheel change detection task?
Your description sounds a little bit like Experiment 3 from 

Hollingworth, A., Richard, A. M., Luck, S. J. (2008) Understanding the function of visual short-term memory: Transsaccadic memory, object correspondence, and gaze correction. Journal of Experimental Psychology: General, Vol 137(1), 163-181. PDF

See Fig. 7 on page 172 for a picture of the display utilized in this experiment.