Junglesteader,
Are you located in Nepal? Switzerland? If you'll put a location in your profile, it will assist other members in answering your questions.
My experience is that the final color must await either kilning or at least 1 year of aging. The implication of the final color depends on the variety, its growing conditions (sun, shade, etc.), the class of the variety (flue-cure, filler, wrapper, etc.) and the stalk position.
Shade grown, a leaf will usually be lighter in color, and thinner than if grown in full sun. Light colored wrapper may be stronger than dark colored filler. Some darkly colored filler may be quite mild in strength, though rich in flavor. And, as always, lower stalk position is always lighter, milder and has lower nicotine than higher stalk positions of the same variety grown under the same conditions.
As an example, PA Red, which is a filler variety, should finish to a reddish brown. Nicotine is moderate, flavor is full. If PA Red upper leaf finishes to a dull, light brown, it has likely experienced improper curing conditions, and may be harsh. FL Sumatra, a wrapper variety, usually finishes to a deep brown, but always remains mild.
I would generalize to assert that among all varieties, the correlation between color and strength is only a loose one. Within a single variety, darker sometimes indicates a fuller flavor and aroma, and possibly higher nicotine, though this is not always the case.
The top leaf of Hickory Pryor, which kilns to nearly black, is smooth, mild, and relatively low in nicotine.
Bob