Pretty quickly, I noticed the custom touch you put on exit pop-up menus, and the renpy quick menu at the bottom of the screen. That's a nice font. I don't even know how your game is supposed to feel yet, but it helps it feel like *something* for sure.
There's a prevalently soft, somber mood, strengthened with the color scheme and stakeout/partnership context of the story.
I take it you used imagemaps for the point-and-click "investigation" section of the game? That's SO cool, I hadn't ever considered ren'py being capable of replicating that functionality. The music change (to an upbeat jazzy tune, I think?) was very good as well -- I immediately got the hint that it was time to Interact with the game differently.
.... However... I seem to be stuck here. I believe the key will be used to unlock the small drawer, and I found my partner's badge in the couch, but I don't seem to have an inventory system with which to access/use them...
I hope I'm not missing out on anything. ^^ I found A Shade of Blue overall to be intriguing, and am fairly certain that my partner will confess her undying love and attraction to me if all goes well.
The art and gui are lovely and to-the-point, which I find comforting to look at. I love seeing Tanya's sprite pop up to make commentary towards the end, and that very PW/GT reaction of "Why did I try to put my hand in there...?" (Or something similar. It made me smile.)
I'm looking forward to seeing even more of your process in your devlog!