I think your exploration is a bit shallow and you might have a bit of an ego/arrogance problem. ( shocking in this profession I know )
I don't know you and you might be the nicest guy btw, the ego-arrogance just applies to this particular project and how you are presenting it, remove yourself from the problem and let me show you what I mean:
Let's start with the exploration part: "I hate open signs" , ok tell us why you hate them.
a blue and red glow in every store ignored by everyone
Says who ?, what research have you done ? In more than one occasion I've driven around a block looking for the open sign on a restaurant or a pharmacy, or a red lantern ; )
For the larger population the red “OPEN,” screams “GO AWAY”.
Ehh no, red light does not spoil night vision and also represents about 64% of our available cones ( green~ 32%, blue ~ 2% ), so it is a convenient sought after color for multiple important circumstances.
Giving no other hint what its message is to a customer (with Monochromacy-Achromatopsia)
I dispute this,light intensity is preserved ( due to rods which are tuned for that), so it would look glowy (open) vs non glowy (close), I would go find someone with Monochromatic vision and ask them if they have any problems with the open signs and present their testimony, they probably have other problems though, how about the blind ?, people in wheelchairs ?
In general I think you are just conveniently choosing or making up information to fit your solution while ignoring other aspects that might conflict, that is a nasty bias to have as a designer and as I said it's just my impression and I could be wrong.
The solution I think fails , but again, I am just one person, so I asked 6 random customers on a Starbucks just now what do they thought of the sign if they saw it on a window (the red one) , their answer was that something bad had happened inside, that there was an accident ahead and that they shouldn't enter or some variation, they all looked puzzled with the blue one, but one ventured there was a promotion of some sort, this research took about 3 minutes and required nothing but a smile and an excuse me can you help me with something, what testing have you made ?
I also think you fail to understand the core problem and opportunities, it is not that one person finds the sign ugly ( we all probably do ) , but rather that we still don't have a reliable system for informing costumers of changing hours at one level as well as communicating with them other relevant information, the sign I think becomes irrelevant at this point, but you were already invested, not sure if you realized this.