var monthSale = 0;
var monthSaleZj = 0;
var monthSaleZf = 0;
var yearSale = 0;
var yearSaleZj = 0;
var yearSaleZf = 0;
if(monthSaleZj < 0){
$("#monthSaleZj").css("color","red");
$("#monthSaleZf").css("color","red");
}else{
$("#monthSaleZj").css("color","green");
$("#monthSaleZf").css("color","green");
}
if(yearSaleZj < 0){
$("#yearSaleZj").css("color","red");
$("#yearSaleZf").css("color","red");
}else{
$("#yearSaleZj").css("color","green");
$("#yearSaleZf").css("color","green");
}
<p align="center">
<font face="黑体" size="4"> 月累计</font> :<label id="monthSale"></label>箱
<font face="黑体" size="4"> 年累计</font>:<label id="yearSale"></label>箱<br/>
同比:<label id="monthSaleZj"></label> <label id="monthSaleZf"></label>%
同比:<label id="yearSaleZj"></label> <label id="yearSaleZf"></label>%
</p>