This version of Unity is unsupported.

TextureImporterSettings.swizzleA

public TextureImporterSwizzle swizzleA;

Description

Specifies the source for the texture's alpha color channel data.

By default, values for the imported texture's alpha channel come from the source image's alpha channel. To reorder or invert color channels at import time, change this to another value of TextureImporterSwizzle.

Additional resources: TextureImporterSwizzle, swizzleR, swizzleG, swizzleB.