Many people build sukkahs out of untreated 2x4s. While I understand the aesthetics of leaving them raw and unpainted, emphasizing that it is a temporary structure, is there any reason why you should not paint them? They would last for more years (still taking it down each season), especially if you had several rainy years. Could one apply latex paint to the main members of a sukkah (not necessarily the schatch) without invalidating it?
The Avnei Yashfei 3:64:4 discusses this . The sukka walls do not have to be gidulei karka,so there are no issues if painting the walls of sukka. However ,there is a discussion about painting schach if it falls into the rabbinic pesul of nishtaneh tzurasan(change of original form) ,and won't look like gedulei karka (plant based material).
The Avnei Yashfei goes on to explain that just coloring the schach doesn't fall into changing the form since everyone can see that it is a plant based. He does note that a formacia covering should not be used (even though a case could be made for it).
He notes that Rav Chaim Kanievsky witnessed the sukka of the Chazon Ish who had painted schach.
Rav Eliyashiv also held that coloring is fine ,but formaica should be avoided.
Text of some of the teshuva :
Gaon Echad is Rav Eliyashiv:
Yes you can paint or treat the walls. It is difficult to ruin the walls vis-a-vis the laws of succot.... Usually things like Height are an issue for example (Gemara Succah 2a).
I think mostly it is aesthetic and also that the first time you build a succah is near to succot causing issues with the smell of paint. Though nowadays they have odor free paint.
It is normal for Jews to have a "permanent" structure on their porch and usually treat it if it will be up the whole year. Usually this "structure" is just the skeleton and not the walls.
As a sidenote: most people will avoid doing things to the rafters lest there be an issue of something Mekabel Tumah supporting the Schach directly. Not saying paint would be an issue, but I could imagine people being nervous about it.