Hey, first post but I thought I could help.
There is no colour in the old RAL system called Sandgelb - it doesn't exist. After the order to paint Tigers in Dunkelgelb (of which there are 3 RAL variants) no Tiger (or pretty much anything else for that matter) would have left the factory painted in anything other than Dunkelgelb until the next order came in for factory applied 3 tone in Autumn 1944. Red-brown and green was also supplied but usually applied by the depot, crew or maintenance sections in line with the regiment/divisions requirements. Even then many just went into combat painted in the colour they arrived in.
Your Tiger 250251 - When it was made and what it was initially painted could be a moot point (although its likely it was painted in Dunkelgelb - its certain the first 3 tanks delivered to Großdeutschland 3rd regiment were grey though). This is because just prior to Kursk/Citadel, Großdeutschland Pz Regiment III crews painted all their tanks yellow anyway with green spots/lines.
As for the hatch, I have no idea but the rest of the tank internally would have been painted in an Ivory colour (RAL 1001).