Yes, pH of the soil affects the colour of flower.
Flowering plants grown in acidic soil (pH<7) bears blue flowers or at has a blueish tint.
Whereas, Flowering plants grown in Neutral (pH=7) and Basic (pH>7) soil bears pink and red flowers.
A plant's flower color is determined by a complex balance between chlorophyll, beta carotene, flavonoids,etc in particular pH of the soil to give out vibrant colors like red, blue, pink, yellow,etc.
