Sorry for not giving a comment until now, but its near bedtime here in Denmark :)
It took me some time to figure out the difference of entry #73 and #76 until I discovered the shadow, which actually highlights it better. In relation to all four, mind dark and SEC yellow Works best in my opinion. The logo part Works best with one color up and another Down, like #76 and #73. One option could be to add a light mirroing, bottom Down. Not sure if it would Work, but could be an option.
It took me even more time to actually get the logo, but as I see it now, its a face looking Down, with a man inside thinking out of the brain, is that correct seen?
Have to say its really great when I finally got it.
As for #78 its better than #77, but the thinking bubbles in connection with the shield makes it look like there is a spider on top.
I will make more comments tomorrow morning as I'm on my way to bed.