How to get the colour you want....

[imeg]

Hello, hopefully someone can put me out of my misery here... I just can't seem to get the 'colour replacement brush tool' to paint the colour I have selected. I'm sure there is a simple explanation that I'm just too stupid to have figured out! I've attached a picture to explain what I'm talking about.

Running along the bottom of my photo is the roof of a football stadium and it is a dark green colour. Above the stadium is the leg of a crane which is yellow. So for the purposes of asking this question, say I want to change the colour of the crane from yellow to the same shade of green as the football stadium. I used the 'colour picker' tool to select the stadium roof, however, when I began painting the crane leg it instead gave me this neon/light shade of green instead of the dark green that I'd actually selected. 

Does anyone know why Affinity Photo does not apply the selected colour but instead a different one?

[Old Bruce]

Just now, imeg said:

I want to change the colour of the crane from yellow to the same shade of green as the football stadium.

The Colour Replacement Brush is actually a Hue replacement brush. It cannot deal with the relative light/dark difference.

[BlueLiner]

Try an HSL adjustment instead. click on the yellow dot, sample the yellow with the picker and then adjust the HSL sliders. I quickly cam pretty close:

 

 

[imeg]

Thanks for taking the time to reply and include pics... always easier to follow when it's explained so well. Thank you

[BlueLiner]

As an aside, you may want to mask the HSL so that it does not effect the colors outside of the area you wish to alter