I think you are meaning that the grid is visible in buy/build mode. There are no visible auras that I am aware of at all. If you want to place, for example, an aura lamp you can use the grid (G on the keyboard) to work out where the 9 squares would be for the aura item. Thing is you are probably better to build a +3 environment and then just use a few aura items depending on what emotion you want to trigger in your sims. Or use 'reminisce about memory' etc etc
Items with an emotional aura can only be triggered/selected in live mode once you have exited build/buy mode. Obviously items that add to the environmental score don't require 'triggering/turning on', you just have to place them.
If I'm building a house for my world but won't be actively controlling the sims that will live in the house. I place, for example, the aura/mood lamp then later, once the house is complete and I have moved sims into it... I visit the house with my sim and when he is there just toggle on the auras on the placed items as I am playing.
Hope that helps. I found your question a little confusing, probably due to the title of your post...
