IBM EGA Card  -  Problem With 64 KB of Video RAM

Lack of Colours

The highest resolution video mode available in the IBM EGA card is video mode 10h (16 decimal). Understandably, a lot of programs will want to use mode 10h.

But, with only 64 KB of video RAM fitted to the IBM EGA card, video mode 10h can only display 4 colours.
According to the article here, in such a situation, Windows and some programs will select a lower resolution video mode in order to display 16 colours.
There will be some programs that instead select video mode 10h, but the picture quality will be poor because of the limitation of 4 colours.

The answer is to upgrade the video RAM to at least 128 KB (via the optional Graphics Memory Expansion Card). Video mode 10h will then have 16 colours.

But is 128 KB Enough ?

The question becomes, is an upgrade to 128 KB enough, or is 256 KB required?

According to the article here, "You reap no advantage from going beyond 128K unless you have a specialized application that requires the extra video pages."
That article must have been written early in the EGA's lifetime, because there were certainly games that had a 256 KB requirement.

Read the conversation here on the Vintage Computer Forums.
The conversation will convince you, that if you run intend to run EGA games, then 256 KB is 'playing safe'.