The presence of chromogenic substrate gives blue coloured DNA bands on the gel. This statement is not true. Chromogenic substrates are usually used in other techniques.
Ethidium bromide is a commonly used fluorescent dye that intercalates between the base pairs of DNA. It binds to the DNA fragments present in the gel, allowing them to be visualized under UV light.
Bright orange coloured bands of DNA can be observed in the gel when exposed to UV light. This statement is true. After staining the DNA fragments with ethidium bromide, they can be visualized as bright orange bands when the gel is exposed to UV light.
The process of extraction of separated DNA strands from gel is called elution.