Not sure if this is still updated, but I found a plain white paintjob for the Caesar BTT prop aircraft that came with the Apex Expansion.
this setObjectTextureGlobal [0,'A3\air_f_exp\Plane_Civil_01\Data\btt_ext_01_co.paa'];
this setObjectTextureGlobal [1,'A3\air_f_exp\Plane_Civil_01\Data\btt_ext_02_co.paa'];