Buttons

To style all the buttons target the .dx-button-content class. 

.dx-button-content{
     background-color: #fff;
     color: #888;
     border: 1px solid #888;
}

The above styling gives following buttons:

To target only the buttons in the confirm dialog you can write: 

.confirm-dialog .dx-button-content{
      // css here. eg for green border:
      border: 1px solid green;
}

For the command-buttons on the grid-view: 

.gridImageHover{
        background-color: #000000 !important;
        box-shadow: 0px 0px 5px 1px #000000;
        font-size: 20px;
}