Answer: Blue roses are not really blue, but purple with some blue highlights. Breeding adds the indigo blue color but it sometimes doesn't show up until the rose begins to age and fade. There's no scientific evidence that soil pH makes a difference in blue roses, but it's sure worth a try. Have your soil checked and if the pH is not between 5.8 and 6.5, you might want to feed with an acidified fertilizer.
Best wishes with your roses!
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