How valid the state of both select at the same time!

The problem is that when the mouseout event of the select element is executed, it is only evaluating only one element at a time, so it never verifies that the two elements have selected indices other than 0.

For this you must go through all the elements and verify that no element has selected the index 0 of the list of options, here I show you an example of how it would be when validating all the elements:

Eye: You are using Ecmascript 6 syntax, so you should be aware that in older browsers this solution may have problems.

let btn = document.getElementById("btn");
        let list = document.getElementsByClassName("options");
        btn.disabled = true;

        for (item of list) {
            item.addEventListener('mouseout', function () {
                let numberOfValidElements = 0;
                Array.from(list).forEach(element => {
                    if (element.options.selectedIndex !== 0) {
                        numberOfValidElements++;
                    }
                });

                btn.disabled = (numberOfValidElements === list.length ? false : true);
            });
        }

<select class="options" name="" id="">
        <option value="1">1</option>
        <option value="2">2</option>
        <option value="3">3</option>
    </select>
    <select class="options" name="" id="">
        <option value="5">5</option>
        <option value="6">6</option>
        <option value="7">7</option>
    </select>
    <button id="btn">Submit</button>

Well, according to what I understood, I made you a demo.

In the html you assign an id to each select (different)

<select class="options"name="" id="select1">
    <option value="1">1</option>
    <option value="2">2</option>
    <option value="3">3</option>
</select>
<select class="options"name="" id="select2">
    <option value="5">5</option>
    <option value="6">6</option>
    <option value="7">7</option>
</select>
<button id="btn">Submit</button>

Then with javascript you check with the onchange event if any of them has changed.

let select1 = document.getElementById('select1');
let select2 = document.getElementById('select2');
let btn = document.getElementById('btn');

//Por defecto 
btn.disabled = true;

select1.addEventListener('change', () => {
        select1.selectedIndex != 0  && select2.selectedIndex != 0? btn.disabled= false: btn.disabled= true;
})

select2.addEventListener('change', () => {
        select1.selectedIndex != 0  && select2.selectedIndex != 0? btn.disabled= false: btn.disabled= true;
})

I hope it has helped you!