I thought that i could do this:
i[1] = 23; // this is built from a regex
$('select [name="sys_map\\['+i[1]+'\\]"]').css('border-color', '#FF5C5C');
or maybe
$('select [name=sys_map\\['+i[1]+'\\]]').css('border-color', '#FF5C5C');
to select
<select name="sys_map[23]">
quoting the name shows error:
[15:36:27.647] Error: Syntax error, unrecognized expression: select [name="sys_map[1]"