Looking at the screenshot and your code, it seems like the following variable is the one you will use to determine which of the 3 images to display.
$checkSqlRow["LEGIT"]
Your screenshot suggests this variable will contain one of the following values:
weet nie
nee
ja
One option would be to test for those values in an if / elseif statements to determine which image to display. For example, if the green image is to be displayed for "ja" and red for "nee", you could do something like this:
<?php
$checkSqlRow["LEGIT"] = strtolower($checkSqlRow["LEGIT"]); //make sure the value is lower case before testing
if($checkSqlRow["LEGIT"] == 'ja') { echo '<img src="green.gif">'; }
elseif($checkSqlRow["LEGIT"] == 'nee') { echo '<img src="red.gif">'; }
elseif($checkSqlRow["LEGIT"] == 'weet nie') { echo '<img src="yellow.gif">'; }
?>
Note that the image names (and the path) will need to be adjusted to whatever you are using.