46: Colour and Style Q&A: A shape Can I wear dark top, Adding the right contrast with an accessory and can you be a mix of warm and cool?

If you have an ideal value of medium light and medium-low value contrast but are an A shape – can you wear dark tops? 
My young son has warm skin and cool eyes – can he be a mix of colouring?
If I’m neutrals plus 2 colours can I just wear a different coloured necklace to the colour in my top, or do I need to add that colour to more areas of my outfit – such as a bracelet too?