Butterflies and moths, with their diverse wing colors and patterns, serve as excellent models for studying the adaptive evolution of traits. The sequential development of their wings integrates spatial and temporal genetic and molecular information, resulting in complex and striking visual phenotypes. Therefore, the development of Lepidoptera wing colors and patterns is ideal for investigating how evolutionary forces interact with developmental pathways to produce phenotypic diversity. To understand how phenotypic variation connects to an evolving developmental landscape, it is essential to identify and characterize the gene regulatory networks (GRNs) underlying complex color pattern phenotypes across developmental time and evolutionary scales. Recent advancements in sequencing technologies and genome manipulation have provided insights into the mechanistic basis of color pattern development and evolution. However, these studies have been limited to a few genomic loci in a small number of butterfly species. In my dissertation, I address this limitation by investigating and characterizing the previously implicated but uncharacterized genes mirror, araucan, and bric-a-brac within the context of butterfly wing color pattern evolution and development. My goal is to construct a GRN framework that explains the evolution and development of Lepidoptera color patterns. In the first chapter, I show that the transcription factor mirror acts as a selector gene to differentiate a far posterior domain in the butterfly wing, classically defined as the vannus, and has wide-ranging effects on wing shape, scale morphology, and color pattern. Our results confirm that insect wings can have more than one posterior developmental domain, and support models of how selector genes may facilitate evolutionarily individuation of distinct AP domains in insect wings. Our results also suggest that the alula, a small mirror-dependent structure at the base of the D. melanogaster wing, may be an evolutionary derivative of the vannus, and therefore that the D. melanogaster wing blade is a solitary remigium that represents only a fraction of the archetypal insect wing. In the second chapter I focus on the Iroquois complex gene araucan. Butterfly wing colors result from pigmentation or the interaction of scale ultrastructure with light, producing iridescent blue and green colors. The only genomic locus causally linked and functionally validated to cause iridescence is the transcription factor optix. I show that mutations in araucan phenocopy a gain-of-iridescence mutation like optix mutations, suggesting its role in regulating iridescence by altering laminar scale thickness. Additionally, araucan positively regulates purple iridescence in the eyespots of buckeye butterflies, turning them shimmering brown when knocked out. In the third chapter I characterized the function of the transcription factor bric-a-brac, previously shown to influence pigmentation in Drosophila bodies and determine ultraviolet-reflecting scale morphology in Colias butterflies. My findings reveal that bric-a-brac is a major regulator of the color palette across Lepidoptera, switching and fine-tuning color pigments across species that diverged about 100 million years ago. Furthermore, I investigated how the downstream GRNs controlled by bric-a-brac vary across multiple Lepidoptera species, providing insights into the evolutionary shaping of these GRNs with respect to color pattern development.