so are both the pics, top one is the colour you want and the bottom is the one your at now?
if it was just the particle size you could high speed mix it to break up the pearl to simulate a smaller size but i suspect other aspects are throwing you off.
more like because the base coat is visually looking darker, the pearl has a better contrast so it looks like their bigger as you can see them easier, just a thought.
also your undercoat colour matters, if your just going down the fewest coats of paint possible! which what you have there is quite grey/blue almost a purple hue from the picture earlier on from the primer so with that you either apply loads of top coats which will be very thick,costly and probably still abit off colour or you should apply a few good solid white under coats first to lift the colour to help the top coat out.
thats what you need to do, but now you have a choice, keep the path and apply a lighter and brighter colour to off set the darker red (which to be honest is digging further down the hole) then you might have to do all the other panels and tank the same way so at least they match or you apply loads of white coats and try the red again with the under layer lighter...might not be perfect but a damn sight better... upto you.
also to note the pearl colour and type (if its a organic or synthetic, plated or coated) will make a massive difference.