When I started using Sketchup, one of the first things that made me wonder, was why there were two surfaces of different colour, since there was no difference when I design something.
I must admit, that only the last few years i began to wonder what was the real reason that this was happening, when I had evolved my designs and had started to face problems that occured for that exact reason. The first issue I had was with the renders in Vray. I was importing a material on the «back» surface of Sketchup, and when i tried to render, it was not producing the properties i had given to my model, or even sometimes, was not even showing the material at all. Another issue, might come up when we want to export our model to another format, in order to use it in another software. In many other softwares, the «back» surface of Sketchup, cannot be recognised, and it is shown as blank. At this point, i must say, that as softwares get better, issues like these will not exist for a long time. Anyhow, it is always better though, to design on the «front» white surface.
As we can see in the picture above, in Sketchup, we have two surfaces, no matter how complex our design is. By removing one side of the cube, we can see in its interior all the «back» surfaces, and on the exterior we have all the «front» surfaces.
Sometimes, even by accident, we might have some surfaces facing the wrong side, than the one they should. As we said before, it is better to work on the white surfaces, so now we will see how to flip a surface over. It is very simple, and it can be done only with two moves. Firt of all, we choose the surfaces we want to flip, then we right-click on the them, and finally we choose the «Reverse Faces» option. As we can see the surfaces now are flipped.
There is a possibility, that someone might not want these two specific colours for the «front» and «back» surfaces, either because they don’t like them, or for presentational reasons. The way to change them is very easy. On the Menu bar, we click the Window button, and we choose the option Styles from the drop-down list. Then a new window pop up, and on that window we click on Edit, then from the icons underneath we click on the second one that is called Face Style, and by choosing the small box with the colour of the «back» surface, right next to Back Color, we can change its colour by choosing another one from the colour wheel. Then we click ok, and the colour is changed.
You need to remember, that if we change the colour of the surfaces, we will change the colour of every surface in the file we are working on.