You need to modify the template you are using as the default. Open a fresh SketchUp session. Make the desired changes to Profiles (set them to 1 if you don't like the heavy edges but leave Profiles turned on) and change colors to suit. I'm not sure what you are referring to as yellow and bluish but all colors can be modified. Make sure you update the style by clicking on its thumbnail in the upper left corner of the Styles window. Then use File>save as template... to save the new template. Make sure Use as default is ticked. From then on, when you open SketchUp, it should look the way you want it to look.

No. It's not. I was just using your term. 😉

You're welcome. I hope that does what you need.