well they aren't supposed to be black i said you can see part of it in them

that plant only had 3 waterings and they went that dark.. and in the second pic you can see where the dye is going through the leaf veins of the young-ling...
if you do it the entire life of the plant you get what i call nearly black and the buds come out that way also
don't believe me try it lol it doesn't hurt anything and its a fun experiment .. i use McCormick black food coloring but any food grade black dye will work but don't do it unless your plant needs more heat because it will make them run hotter becuse the leaves will absorb more becuse of non reflective coloring