Target your layer and click the black/white circle icon in the Layers palette. Select Solid Color and choose the color you want for your stitches, click OK. Then clip that solid color to your stitches layer. Play with the opacity/blending modes of the color layer to fine tune the look.
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Cassie
My Gear: Nikon D300s w/18-200mm VR & 50mm 1.4
Software: Adobe Photoshop CS4, PSE 6, Lightroom 2