This perspective article provides an overview of the basic structural and optical properties of lead halide perovskite (LHP) colloidal nanocrystals (NCs), highlighting their differences and similarities with conventional II-VI and III-V semiconductor quantum dots. It emphasizes two key issues: the advantages of defect tolerance and the need to improve stability under environmental conditions. The article discusses the blue-shifted emission from CsPbBr3 NCs and explores synthetic strategies for fabricating stable LHP NC materials with emission in the red and infrared parts of the optical spectrum, focusing on mixed-cation compounds guided by the Goldschmidt tolerance factor. The defect tolerance of LHP NCs offers inspiration for searching for similar attributes in other heavy metal-free compounds. The article concludes with a discussion on the potential applications of colloidal LHP NCs in backlighting for liquid-crystal displays.This perspective article provides an overview of the basic structural and optical properties of lead halide perovskite (LHP) colloidal nanocrystals (NCs), highlighting their differences and similarities with conventional II-VI and III-V semiconductor quantum dots. It emphasizes two key issues: the advantages of defect tolerance and the need to improve stability under environmental conditions. The article discusses the blue-shifted emission from CsPbBr3 NCs and explores synthetic strategies for fabricating stable LHP NC materials with emission in the red and infrared parts of the optical spectrum, focusing on mixed-cation compounds guided by the Goldschmidt tolerance factor. The defect tolerance of LHP NCs offers inspiration for searching for similar attributes in other heavy metal-free compounds. The article concludes with a discussion on the potential applications of colloidal LHP NCs in backlighting for liquid-crystal displays.