Created attachment 200306 [details]
Textarea with wrong rendered foreground color
The summary pretty much speaks for itself.
If you do not specify a foreground color for disabled textareas, Webkit will lighten up the current foreground color to visualize the disabled status.
Adding "background-color:transparent" to such a disabled textarea alters the behavior for certain grey tones. For example "color: #55555;" works as expected but "color: #A0A0A0" results in nearly white text to be rendered instead of a light grey tone.
So with "background-color:transparent" WebKit does some wrong color calculations during rendering.
I have attached a demo that illustrates the problem. It contains a set of 4 textareas with different foreground colors. This set is repeated 4 times (enabled/disabled with and without background-color:transparent) and in the last set the last two textareas behave wrong (color is too bright).
Discovered using Safari on Mac OS 10.7 & 10.8, as well as Webkit Nightly for Mac.
Interesting workaround for this -- WebKit interprets `transparent` as `rgba(0,0,0,0)`. If you set background-color to `rgba(255,255,255,0)` instead of `transparent`, results are as-expected.
This bug is also present on <input> elements