壁は内側が白くて外側は緑です, why 内側が白くて use が and 外側は緑 use は


why 内側が白くて use が and 外側は緑 use は

why not 壁は内側は白くて外側は緑です or 壁は内側が白くて外側が緑です?




That's because the sentence wants to emphasize that it is 内側 that has 白 color.

If you just want to tell information about wall colors, the following sentence
is the most natural.

壁は内側は白くて外側は緑です

English equivalent is "The inside wall is white, the outside wall is green."

If you are asked which side of the wall is white, then you'd like to emphasize
it is 内側 that is white, so the following sentence would be natural.

壁は内側が白くて外側は緑です

Engish equivalent is "It is the inside wall that is white, and the outside
wall is green."

If you are asked which side of the wall is green and which side is white, then
you'd like to emphasize both 内側 and 外側. So this would be natural sentence.

壁は内側が白くて外側が緑です

English equivalent is "It is the inside wall that is white, and it is the
outside wall that is green."

