Problems with light map compression

We are facing an issue with light map compression in Unity, please refer the images below

When we switch the format from true color to compressed and also the size of the map some green artifacts appear all over the map, we are looking for a solution keeping the compression as it helps us control the size of the overall build,
would really appreciate if we can get some help on this.

Old question, but still valid. On Android IHMO the best compromise for lightmaps would be ASTC_RGB_6x6 , but of course you can use it only on devices with OpenGL ES 3.0 support and A8 and up on Apple.