The following worked for me. I using class attribute instead of ID to match multiple color pickers.
<script type="text/javascript">
jQuery(document).ready(function($) {
jQuery('.color-picker').on('focus', function(){
var parent = jQuery(this).parent();
jQuery(this).wpColorPicker()
parent.find('.wp-color-result').click();
});
});
</script>
My Widget form is set up like :
<p>
<label for="<?php echo $this->get_field_id( 'font_color' ); ?>" style="display:block;"><?php _e( 'Font Color:' ); ?></label>
<input class="widefat color-picker" id="<?php echo $this->get_field_id( 'font_color' ); ?>" name="<?php echo $this->get_field_name( 'font_color' ); ?>" type="text" value="<?php echo esc_attr( $font_color ); ?>" />
</p>