Henthymes, they grow up to look almost solid in color (black or lavender). You will see faint white tips on the lavender, but it doesn't stand out as much as it does on a black bird. You can tell the difference between a full grown lavender and a lavender mottled by the shank color. Pure lavender have slatey/bluish legs all the way down. Mottled lav have white shanks with some speckles of blue on them..but mostly white. I would imagine after the first moult, the mottling would be more pronounced in the plumage as it is typically. Prior to that they are hard to tell apart.