The regular power supply is 12V DC attached to the side of the laptop. This power is used to charge the battery. Toshiba will refuse to work even with the power supply if the battery is not charged. As all batteries will be dead at this age, the only way is to attach the power supply instead of the battery. There are 6 battery cells, so the battery voltage should be 9V.
It looks like 0.6A was the maximum current observed, so in case a regular power supply was to be connected, with a bit of the margin, 0.6-1A (6-9W) DC supply should be enough.
The integrated display is monochrome CGA with 4 shades of gray (or actually blue).