Bold Leopard Geckos
Bold makes the black markings on a leopard gecko much darker than a normal, regardless of the underlying pattern. Because this is the source of named lines like Bold Stripe, Firebold, Bandit, and Halloween, you should ask both how dark a gecko is and which line it belongs to.
About the Bold gene
Bold is a line-bred trait in leopard geckos that makes black markings darker than those of a normal. It describes pigment rather than pattern on its own. This trait matters most in the hobby as the foundation of the named bold lines where most of the selective work on dark markings has gone.
Appearance
The Bold trait gives a leopard gecko markings in a heavier, deeper black than a normal one. This trait does not fix the pattern. Bold geckos appear in striped and jungle forms, and the named lines add their own marks on top. When crossed with the striped trait, it gives the Bold Stripe. This carries two heavy dark stripes down the back.
Genetics
Bold is not a single gene but is polygenic. It is kept by choosing the darkest animals over several generations, so there is no het and no super form. You will find it listed as Bold and Pos Bold. Other lines are built on it and sold under their own names. These include Bold Stripe, Firebold, which is a line of tangerine bolds, and R2, GGG and Extreme Bold. It also forms the basis for Halloween, which adds a mask to the head, and Bandit, a bold line with a dark band across the nose. Bold is also worked into tangerines and Tremper albinos. This is where names such as Bold Tangerine and Bold Tremper come from.