Makes it more difficult to diagnose because we don't know the variety. The leaves are quite dark green for a hydrangea, and also rather sparse, seemingly. Note that flower colour change (from pink to blue, or the other way around, or from blue to a sort of faded lilac) is an indicator of the ph of the soil, but this is only true in Hydrangea macrophylla 'hortensia' varieties. Yours, though, looks more faded, like the flowers do at the end of the season, as they start to dry.
Hydrangeas generally prefer dappled shade, though some tolerate a fair bit of sun, and they like moisture retentive, but not waterlogged, rich soil. As you only planted them last year, I'd assume this is a watering issue, given that they're in full sun. If you'd had a very hot year with blazing sun, that might have faded the flowers like this, but infrequent and insufficient water supply would have a similar effect. Given the scarcity of foliage (unless there's more lower down, out of shot, which is lush), increase watering. Best to water a lot and infrequently (once a week if its dry) rather than a little daily. If you didn't enrich the soil before planting, a mulch of good composted material (animal manure compost or good soil conditioning compost) applied in spring around the base should help.