I usually don't go by the suggested paints. Get a few photographs of a Shuttle stack, and get paint that matches the colours you see in the pix.
The black tiles, are more like a dark grey. The white tiles aren't pure white, they're more like a very light grey. The engines are more gunmetal than silver, and the Fuel Tank .... well, that really varies. From brown to light tan, with many different shades on the same tank.
But for a start, the colours you've got, will work. Mix 'em and match 'em and your shuttles will look just fine.
Pete