Why is that my header color not appearing once previewed?

I've added the CCS using the following codes:

.form-header {

    font-size : 30px;

    color : #5DBCD2;

}

The change appears when I'm in Advanced Developer and Builder, but won't change in Preview or once it's published...

Thank you

Add !important after the "color : #5DBCD2" and that should force the header to change to the preferred color.

ex.

.form-header {

    font-size : 30px;

    color : #5DBCD2 !important;

}

Let us know if you have any questions or if you need further assistance.