Global colour switches to a non-existant gradient with different colours

Hello, I am creating a two tone map that uses a single global colour (some countries are 100% of the colour, some are 40%). The dark blue is 100% (0/15/123, global), when I reduce it to 40% tint (or any other amount) it converts it to the gradient shown. How do I disable this and just get the 40% colour?