For all of us using bootstrap, you can change the style by adding the "disabled" class and using the following:
HTML
<button type="button"class="btn disabled">Text</button>
CSS
.btn:disabled,
.btn.disabled{
color:#fff;
border-color: #a0a0a0;
background-color: #a0a0a0;
}
.btn:disabled:hover,
.btn:disabled:focus,
.btn.disabled:hover,
.btn.disabled:focus {
color:#fff;
border-color: #a0a0a0;
background-color: #a0a0a0;
}
Remember that adding the "disabled" class doesn't necessarily disable the button, for example in a submit form. To disable its behaviour use the disabled property:
<button type="button"class="btn disabled" disabled="disabled">Text</button>
A working fiddle with some examples is available here.