> 24 X 40 text, @ 320 x 192 monochrome
About that AFAIR... 1-bit palette of two arbitrary colors.

> and 160 x 96 with 128 colors.
No.
Atari at its best supported 16 predefined colors (in some 80x192 or so, damn long flat pixels), 4 arbitrary colors in 130xsomething (I don't remember already) and 16 arbitrary colors in decent resolution almost like that of the text mode in something that actually -was- a text mode, but with character fonts arbitrarily definiable so they could be used to build graphics (this was the favourite mode of game writters, with "fonts" for all kinds of bricks, backgrounds, pickups etc, player and enemies done using "sprites".

Actually it -was- possible to reach all possible 256 Atari colors at once, or more than the limits defined, but that was a hack. Atari had a chip for displaying pixels of given color index, and a chip for defining which index corresponds to what actual color. And you could redefine the actual color of the pixel "on the fly", during displaying the image, so i.e. you could display a row of pixels with 4 colors from one palette, then redefine the palette and display the next row with completely different palette. The process of redefining a color was so slow though, that you couldn't bundle 8 differently coloured pixels in a row, simply changing the color definition for a color took time needed to display several pixels.