Highlight cells to show time has passed, will pass soon, and has ample time

First, let me thank you for helping me to solve this question. I hope im posting it in the correct forum.

What I want to do is have a cell highlighted like a stop light, based on promise time, versus the current time. I attached a sample to this post.

The idea is to know if a promise time, given to a guest, will be met. If it will not be met, then we can inform our guest for damage control.

Highlight RED, time has exceeded/passed PROMISED TIME.
Highlight YELLOW, time is about to exceed/pass PROMISED TIME. (<59 minutes till promise time)
Highlight GREEN, >1 hour TILL PROMISED TIME.

Id like to understand how you came up with the formula if you could explain it to me. That way I can adjust the highlights as my needs change. In the future I may want an additional color to inform me of <30 minutes to promise time so I can prepare for a possible failure.

For the YELLOW highlight id like it to be 59 minutes till promise time. This way I know when I have less than one hour to keep our promise.

Finally can I have this shared in my department so anyone can view it from their terminal. We have shared drives that I could have this sheet stored. Will it be "live" as I update it when each guest comes in? If not how can I make it live?