Nah, RGB works because it's not encoded, only the refresh rate changes. Composite, SVideo and Component are encoded so that everything can fit in a single wire. NTSC and PAL have different incompatible Chroma encoding. Often what happens when a TV made for a region receives a signal made for another is that it only displays the Luma (B&W) part of it, which isn't encoded and common to both standards. Sometimes a TV can display a foreign encoding only on a specific input, but that was mainly for older sets, or so I thought.
Lots of purple looks like on the PS2 whenever RGB or Component is selected in the menu but the other cable is used. Purple for one combo, green for the other iirc.
Keep looking in the menus, try to find the service menu, maybe something is deactivated somewhere. Call Toshiba directly or the place where you bought it (any number on your manual), maybe the whole range was misconfigured: the last TV I bought was configured for use in Eastern Europe with only Russian, Ukrainian, Polish and other weird alphabets were selectable, with no trace of English or any other western languages. The seller laughed at my incompetence when I explained my problem at the shop, but when I called customer service they had me go deep into the service menu to change stuff and get western languages. They had loads of complaints and they just fucked up at the factory.
[Edit] waitaminute I don't see PAL60 in the manual. Probably an oversight, but there is a possibility the decoding is based on the refresh rate, ie assumes that anything 50Hz is PAL and anything 60Hz is NTSC. The PAL console with an American game would still output PAL, but at a faster 60HZ? I don't know much about the N64 but that's how I'm assuming it should work. Call the helpdesk, but don't give them that info directly. PAL60 is a thing (in Brazil), so TVs should manage.