Depends which one you have - there are a few things called 'firebush'. If it's an embothrium coccineum, seed raised ones can have flowers of other colours, such as yellow or white. The (normally) red flowers give it the common name of Chilean fire bush. The leaves stay green.
A trowel in the hand is worth a thousand lost under a bush.
The photo, it looks like a Pieris shrub. Only new leaves that forms start off red and then matures green. Looking at your shrub, there is no new young growth yet. If it's finished flowering, you can always give them a light prune, and that should encourage new leaves to grow.
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The new leaves in Spring will be red, although that should have occurred by now.
When you don't even know who's in the team
S.Yorkshire/Derbyshire border