How do I stop Chrome from yellowing my site's input boxes?

Set the CSS outline property to none.

input[type="text"], input[type="password"], textarea, select { 
    outline: none;
}

In cases where the browser may add a background color as well this can be fixed by something like

:focus { background-color: #fff; }

I know in Firefox you can use the attribute autocomplete="off" to disable the autocomplete functionality. If this works in Chrome (haven't tested), you could set this attribute when an error is encountered.

This can be used for both a single element

<input type="text" name="name" autocomplete="off">

...as well as for an entire form

<form autocomplete="off" ...>

this is exactly what your looking for!

// Just change "red" to any color
input:-webkit-autofill {
    -webkit-box-shadow: 0 0 0px 1000px red inset;
}