Displaying a Solid Color Box

[pechmo]

I have a report with several bar charts and need to display custom legends below each.  What's the best way to create a set of small square boxes that correspond to the colors of the bars on my bar charts?  I've tried using a Text Item, a Block, and an Image.  All of them do what I want but I want to do whatever is most efficient time-wise because I'll be bursting this report to create 1000s of PDFs and every millisecond counts.