[Fix] fixes #342: creating patches with literal color errors

Fixes issue #342

Minimal example:

    x = [2 3; 2 3; 5 7;5 7];
    y = [1 10; 2 11; 2 11; 1 10];
    patch(x,y,'red')
    matlab2tikz('patchMultipleLiteralColor.tex','standalone',true)