Malus crabapple is highly regarded for its ornamental and garden applications, with leaf color changes serving as an essential indicator of aesthetic appeal. Despite this significance, studies focusing on crabapple leaf color transformations, particularly the fading of purplish-red hues, remain limited. This research investigates the physiological and molecular mechanisms driving leaf color changes in crabapple through physiological, transcriptional, and metabolic assays. Leaf color was analyzed across 86 crabapple varieties, with three representative varieties in different color development paths (the color change from young to mature stage) selected for detailed examination of gene expression and metabolite accumulation within the flavonoid biosynthetic pathway. Our findings revealed greater variation in young leaves compared to mature ones, along with higher stability in the 'Purple to Purple' (P-P) color path compared to the 'Green to Green' (G-G) and 'Purple to Green' (P-G) paths. The comprehensive analysis highlighted anthocyanins, particularly pelargonidin and peonidin 3-glucoside in green crabapple leaves and cyanidin in purplish-red crabapple leaves, as central to leaf color regulation. Transcriptomic analysis revealed that the fading of purplish-red is attributable to decreased accumulation of total anthocyanin and degradation of cyanidin. This process is governed by the down-regulation of anthocyanidin synthase (ANS) gene and the up-regulation of the anthocyanin degradation gene, peroxidase (PRX). Additionally, two transcription factors potentially involved in the regulation of cyanidin biosynthesis and two transcription factors regulating pelargonidin biosynthesis were identified. This study identifies candidate genes influencing anthocyanin accumulation in purplish-red leaves, providing a foundation for future investigations into leaf coloration mechanisms and crabapple breeding efforts.