OB, Great tip! My nucs were mixed between 10-frame gear of various heights, and not more than 5 hives facing same direction at any place. Also a few colors of entrance reducers. All have landing boards.
I have R-5 pink foam under nucs & nucs newly moved to 10-frame equipment; black beetle traps under the larger hives. I hoped that would distinguish them. Still, it may not have been enough distinction.
Probably doesn't help that my area is saturated with bluejays swooping through the apiary area, they eat on the run.
One failure was combination bee and beek error. I try to space the frames apart a little in the egg section of the nest. Still, the bees made burr comb around the Q cell, and connected the Q cell wax to the next frame....which sadly I discovered when I carefully removed the adjacent frame. The wax tore... and there was a snow white queen about 10 days old. Both me AND the bees made that little whining noise, you know the sound.....