masked input plugin placeholder color

I'm using the jquery plugin masked input, and when the placeholder of the plugin is active, I want it to change the colour and didn't take the input color. Is there anyway to do it easily?

This is my jquery code:

$.mask.definitions['A'] = "[A-Z]";
$(".accountnumber").mask("AA99  |  9999  |  9999  |  9999  |  9999  |  9999", { placeholder: "ES00  |  0000  |  0000  |  0000  |  0000  |  0000" });

Thank you very much.