DIV does not open in browser CHROME and IE

I'm trying to solve a CSS problem in my development:

HTML:

I created a responsive DIV with 1 COLUMN (GRID of 6) for a specific content section. I already put text inside this one.

CSS:

I created a class to stylize this DIV

#saldos{
    background-color:FFFFFF;
    height:200px;
    display:block;
}

The result is none in the browser, only text appears, but no background. I think that some parent class is preventing the result that I intend in the SON.

How do I find out what is happening? I've already been in inspect element to see what might be influencing this CSS block.