Mobile and tablet devices button style

I have a simple css defining the color of a button. However, the style is applied on desktop and on some devices (Huawei phone for example), but on iPad the button has default color and on Samsung it is red.

Here is the code:

button.close-post.done {
  color: #fff !important;
  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none; }

Thanks In Advance!