So from what I understand, you want to change all inputs with green color text to grey. If that were the case, you would want to get the elements in question by doing the following:

var greenInputsArray = document.getElementsByClassName("my_inputs");

And then you could loop through the array and if the color is green, you can change the color to grey as follows:

for (var i = 0; i < greenInputsArray.length; i++) {
    if(greenInputsArray[i].style.color == "green") {
       greenInputsArray[i].style.color = "grey";
    }
}

You need the style.color or getComputedStyle

The style.color is undefined if not inline

const getColor = ele => ele.style.color || window.getComputedStyle(ele).color;

document.querySelectorAll(".my_inputs").forEach((ele,i) => {
  const color = getColor(ele);
  console.log(i,color)
  if (color === "green" || color === "rgb(0, 128, 0)") {
    ele.style.color = "grey"
  }
})

#id1 {
  color: green;
}

<input type="text" style="color: green;" id="id2" class="my_inputs" value="stuff" />
<input type="text" id="id1" class="my_inputs" value="stuff">
<input type="text" style="color: green;" id="id3" class="my_inputs" value="stuff">
<input type="text" style="color: red;" id="id4" class="my_inputs" value="stuff">
<input type="text" style="color: green;" id="id5" class="my_inputs" value="stuff">

Just use

var elements = document.getElementsByClassName('my_inputs');
for (let a=0; a < elements.length; a++) {
    if (elements[a].style.color == 'green') {
        elements[a].style.color = 'grey';
    }
}

This will loop through the elements and if it is green, turn it to grey.