Changing border-color of image

Changing border-color of image

In my css all images are formatted with a border: border: 1 px solid #ffffff;
When I click a button, this image appears in a div:
  1. $("#"+myPictureID).append($("<img>", {src: myImage}));
How can I provide that image with a border: 1 px  solid #000000;
I don't see where to put the css.
Your help would be appreciated,
Henk