We have a big orange letter A on one hive, and a blue-painted circular saw blade on the second. The third will have a green gutter strap. That will make them A, O, and I.
Watching the bees do orientation flights in front of the hives is fun. They clearly study the letters, zig-zagging back and forth in front of them for some seconds. Some bees scan them again when they return, others just zoom in for a quick touch down on the landing boards. I presume experience has something to do with it.
Noticing drlonzo's use of letters, I presume he has Spelling Bees.
On removing the entrance reducers, how much does that matter if you have vented screened bottom boards (specifically the vented Freeman traps)? It strikes me that the limit of ventilation is likely not at the bottom entrance, but at the top. If you just have one little notch on an inside cover and no other top vents, it would still be stuffy in there. I've enhanced the top vents by adding some screened holes to my top feeders. Others prop up the telescoping covers.
I'm leaving my entrance reducers in and have temporarily blocked the extra SBB vents until I see more comb drawn and more bees covering frames in the upper brood box. Our nucs have not built up strong enough for heat to be a problem yet. I moved a couple of frames up from the bottom box to encourage them to work the new box, and don't want them chilled on our cool nights recently. Our hives are pretty close to Ft. Gay, so the difference is hive strength.