bug#21557: 25.0.50; HTML renders text invisible

[Katsumi Yamaoka]

On Mon, 28 Sep 2015 16:14:46 +0300, Eli Zaretskii wrote:
>> +  (when (and (or fg bg) (>= (display-color-cells) 256))

> I wonder whether 256 above should be replaced with a much lower
> number, like 88, perhaps?

256 means `Depth 8 Pseudo Color', i.e., 24bit color (R:8bit,
G:8bit, B:8bit) but only 256 cells in the color pallet, AFAIK.
It matches shr-color.el that calculates colors based on 24bit.
But I don't know what is 88-color system.  Is it not based on
24bit color?  If not, a color shr-color offers will be too dim.