Over in Estonia, Tanel Mehine at the University of Tartu has discovered that "consumers perceive yellow price tags as presenters of discounts" and suggests that "companies have the opportunity to increase the consumer’s reference price and thereby to raise revenues by changing the colour of the price tag without offering an actual discount."
In his study, he only compared the use of white and yellow labels.
I hope in his next study he looks at the impact of red labels that say "price checked weekly" like they use at Loblaws.
Here are two I found this past weekend next to cat food price tags of $0.79 and $0.85. The weekend before, those tins were priced at $0.75 and a few weeks ago they were on sale at $0.55 each.
From these examples and others, I've come to the conclusion that "price checked weekly" means that Loblaws has checked a price and decided they needed to increase it.