How to change colour of vector drawing after it’s finished

Hi all, 

I've finished a few drawings, with vector brushes, but I want to change the colours of some of them. I can't convert to a pixel layer, so locking transparency/ masking is out. I also cant use the fill-a-layer-and-then-use-the-downward-arrow-icon method either, as its flattening the images (almost making them pixelated) even if I've filled the layer above with vector colour...

Any other way? 

Thanks everyone!