You can't for Internet Explorer.
See this comment I wrote on a related topic:
There doesn't seem to be a good way, see: How to change color of disabled html controls in IE8 using css - you can set the input to
readonly
instead, but that has other consequences (such as withreadonly
, theinput
will be sent to the server on submit, but withdisabled
, it won't be): http://jsfiddle.net/wCFBw/40
Also, see: Changing font colour in Textboxes in IE which are disabled