problem with Colour replacement tool

Hello everyone,

I am having an issue with colour replacement tool, where I select a colour eg dark blue as you can see in my foreground colour, and it would display as a wrong colour when I use the colour replacement tool. Here it is painting light blue instead of dark blue. In settings for colour replacement tool at top I have Colour mode, the layer itself is on normal blending mode. Could you please help me to understand what am I doing wrong here?

Many thanks in advance,

Rama

PS:file is 4000 px X4000px, RGB, 8 bit