Space when selecting a characteristic

Hi,

It's just a matter of CSS because the selection border around the color you select increases the height of the color element, and since the other elements float, they float on the right of the element.
To avoid that, just force the height of the elements to be bigger than the height of the image with the border and it will display fine.
You can do that with such CSS:
.hikashop_filter_checkbox {
height: 45px;
}