Is it normal for blueberry bushes to have reddish colored leaves?
It is. I have a low bush blueberry in my side yard and I thought also this is not a fruit shrub. But it is. I bought mine from here and they even have a picture of the same plant showing it's got reddish leaves. https://www.trees-plants.com/low-bush-blueberry/
Blueberry leaves that are new, in stress or are abscising will be reddish. Need to know what you've added, how the are watered, the pH of the soil (that is a big deal), where it is you live, such as what zone, the age of these plants, have they flowered yet?
Otherwise, totally normal. My blueberries are reddish right now as they are putting out new leaves. They turn bright red in the autumn before losing their leaves (abscission). For maximum health your soil needs to be at least 6.0 even 5.5 in pH. Properly balanced fertilizer, plenty of water. Blueberries are sort of bog plants.