Patrick is correct with his description of the interior colour.
Elfinbein (the off-white/ivory colour) was applied to the insides of closed hulls (crew spaces) and closed turrets. It went onto the walls, ceilings over most conduiting, most permanent fixtures - gear racks, ammo racks, kit-holders, step-plates, radio-racks, fan-covers, gun-mounts, gun-breeches and barrels exposed inside the turret.
Floors were usually dark green in the early war and red oxide primer later on.
Heavy-metal drive gear- trannies, brake and steering gear - were often painted satin-black or a dark green at the originating factory, and installed wearing their original paint. Radios were also factory-painted (field-gray, dark green, or sometimes satin black or other colors), and kept those colours when installed into their racks.
A quick note on the inside of the hatches.
In the early war years the inside of the hatches were also painted in the Elfenbein colour. This was quickly changed (1941ish) to the exterior colour of the vehicle as crews learned from bitter experience.
The above a bit of a generalisation for early war tanks but is true of most cases.
I hope this helps.
Good start to the Pz 38t. I'm really looking forward to seeing this progress. It will be great to see a large scale blitzkrieg panzer.