Modern Mansion Building Tips?

I don't think it looks terrible at all! It just still just early in construction. Cool outline.

I wouldn't use more than three different colors on the exterior side. Even with your neutral colors, it might start to get convoluted or busy. Personally, I'd try to stick closer to just two, Only adding a third for smaller hits or extra smaller splash of color.

Here's all the windows you can use other than the large plain ones.
Short walls.
https://i.imgur.com/Ov5fNY7.jpg
Medium walls.
*note the two blue-paned ones are the the same window, you can get vastly different looks by just the style/color
https://i.imgur.com/0eAawuN.jpg
Tall walls.
https://i.imgur.com/9uwDA6Y.jpg

You don't have to stick to black colors -you can go as bright or as colorful as you want. I just thought it would be easier to see in a screenshot. Also, obviously, you wouldn't use all of these. Pick two to three you think go well together and just use those. I usually divide up using all of one type of window on one floor or using only the same type of window on the same type of wallpaper. My favorite "modern" window is the horizontal slots featured in the bottom floor of the images below.

https://i.imgur.com/tlxuu4u.jpg
(black, grey, green)
https://i.imgur.com/2VnPIwG.jpg
(white and green)

You can go dark or light, however you prefer. The top is a three-colored theme, and the bottom is a two. Personally, I believe the bottom works better because there are less colors -even though two of the colors used in the three-color are neutral. Some people use the flat colors for walls on modern buildings, but I prefer to always have something with texture on the exterior -even when it's just paint. (use those splotchy paints). Tile textures are great for modern buildings to give it that modern feel!

If you have Dine Out, you can use bb.showhiddenobjects to access a small horizontal fence (featured in the images above) to put around gardens. Contained gardens have a modern feel to them. I'd stick to blockier garden shapes for your landscaping since your outline has a blocky (yet modern!) feel to it. I'd repeat that shape. Also, tall thin trees usually have a modern look.

Thank you SO much! I will definitely take into account your tips, and I love how much effort and detail you put into this post <3 . I will probably use the same windows you have used because it looks amazing. I will (if I remember) post the end build, thanks so much again!! :) :)

I think a lot of it, too, is playing around with wall textures. Yes, you can keep everything white or monochromatic, but mixing up woods and plaster, etc., adds some dimension.

And landscaping, incorporating decor with the build always helps it to stand out, and fleshes out the look a lot!

Oh yeah, I forgot to say - sorry if this is the wrong section, if it is please tell me and I'll delete the post.