Looks like your pixel selection for your overlay layer was feathered or in some other way you've slight dithering or transparency feathering occurring - this dark ghosted line at the edges is a result of that methodology.
If it were me, I'd be using a recolour adjustment layer for your hue shifts, with masks on that layer to control which chaise-longue strips are colour-shifted, versus pixel-painting new data above - this will both give you a better general result (shadows and highlights will remain correct) and make avoiding that dark line easier.
That said, your base would be better to be white or very light - this will both make colour shifting easier, and will mean that if you do miss a pixel or two in the overlay layer, it'll be really hard to see that against the white background.
Nonetheless, here's a quick run through with your low-res screenshot to explain:
- The basic layer setup:
- Changing the hue being replaced with:
- The mask (started at pixel-selection of your altered image, spent perhaps two minutes after that quickly painting the rest of the mask) used to control the area affected by the adjustment layer:
- end result viewed at correct pixel res given low-res input:
- Oh, and with the requisite white you'd shown - just to demonstrate how the desaturation & lightness controls allow a huge range of achievable final tones:
In answer to comments:
Note: I'm using a recolour adjustment layer with a mask to control its area of effect, and a single base image.
When that result is then exported, and a new adjustment layer with different colours is exported, there is no pixel level movement or difference, as the underlying image is exactly the same - that way I don't have to worry about cutting the image at all... that is the thrust of this method; it's both non-destructive and easily iterated - and that's the main point - easy iteration.
Like so - observe that there is only one pixel layer - the rest is all adjustment layers and their relevant masks - not also each mask can be different - here they're the same for simple expedience:
hope that helps.