Sweet potato (Ipomoea batatas (L.) Lam.) is increasingly recognized as a functional crop due to its rich content of health-promoting phytochemicals. This study compared the phenolic compound profiles of four sweet potato varieties differing in flesh colour (purple, orange, white, and pale yellow) cultivated in three distinct regions of Hungary. The objective was to evaluate the relative effects of pigmentation and growing location on antioxidant capacity. Tubers were collected in triplicate and analyzed spectrophotometrically (UV–Vis) for vitamin C, total flavonoids, and total polyphenols. Statistical analysis using two-way ANOVA and Tukey’s HSD revealed that flesh colour had a significant effect on all antioxidant parameters (p < 0.05), whereas geographic origin did not. Purple-fleshed tubers exhibited markedly higher levels of vitamin C (21.6 mg/100 mL), flavonoids (378.7 mg/100 mL), and polyphenols (37.0 mg/100 mL) compared with the other colour groups. These findings indicate that pigmentation is a stronger determinant of antioxidant potential than cultivation region. The results highlight the promising nutritional value of Hungarian purple-fleshed sweet potato varieties, supporting their use in functional food development and sustainable agricultural diversification strategies.