Can choose colour, but not hue?

Brand new to photoshop and just trying to change the colour of an object.

I've got the Colour Replacement Tool and all the settings ready to go [low tolerance, contiguous limits, continuous sampling, etc]. I select a dark green colour, the correct colour is showing in the display square. I start re-colouring the object and instead of the shade I want, the bright green displayed on the long, thin colour bar to the right of the main swatch comes out.  [see image]

No idea how to switch over the actual colour I want. What am I doing wrong? Thank you.