How add colour to button

[APV Babu]

Hi Every one!!!!

I created one new button "plan document team request" in incident form I want to add 'blue' color for the button 

I am trying with this code but I couldn't

function onLoad() {
changeButtonColor('plan_document_team_request', '#0000FF');
}

function changeButtonColor(buttonID, backgroundColor) {
try {
//Find the button(s) by ID and change the background color
$$('button[id=' + buttonID + ']').each(function(elmt) {
elmt.style.backgroundColor = backgroundColor;
elmt.style.color = '#ffffff'; //make the button text white
});
}catch(e){}
}

[jaheerhattiwale]

@APV Babu Can you please mark as correct answer