Model of car raced by a Belgian driver in the Belgian Gran Prix, hence the yellow color.  Back in the days before F1 cars became rolling billboards it was customary for the cars to be painted in the national racing colors of the country represented by the driver or the team.  Belgium's color scheme was a simple overall yellow (though we can think of several other countries for which yellow would be a much more appropriate national color.)  Germany had silver, though it started out with white.  That lasted until the Mercedes team sandblasted all the paint off their cars to save weight, leaving the bare aluminum.  England's color was green, France had blue, Italy (of course) had red, and the US had white with blue stripes.  We hope there wasn't some unfortunate country somewhere that got stuck with lavender, mauve, or puce.