Validate answers to online quiz
I can be rather quick with the CSS part, use indentation:

.example{
    oneTab: indented;
}


Round one

Then, you Javascript. Again, indentation. After that, I've removed several blank lines which had no purpose

Result:

 $("#vancouver").ready(function() {
    $(".fillBlank").val("");
});

// vancouver quiz answer one
var one = document.getElementById("one");
one.addEventListener("keydown", function (e) {
    if (e.keyCode === 13) {
        valone(e);
    }
});

function valone(e) {
    var one = document.getElementById("one").value;
    if (one === "while") {
        document.getElementById("one").style.color = "green";
    }
    else {
        document.getElementById("one").style.color = "red";
    }
}

// vancouver quiz answer two
var two = document.getElementById("two");
two.addEventListener("keydown", function (e) {
    if (e.keyCode === 13) {
        valtwo(e);
    }
});


/* repeat code for every question */




Round Two

Make use of the short if/else. Example below:

function valone(e) {
    var one = document.getElementById("one").value;
    //                                            Statement    ?  true   : false
    document.getElementById("one").style.color = one==="while" ? "green" : "red";
}
//---------------------------------------------------------------------
// And now save the 'one' element so we dont select it twice
function valone(e) {
    var one = document.getElementById("one");
    //                 Statement          ?  true   : false
    one.style.color = one.value==="while" ? "green" : "red";
}




Round Three

You repeat yourself for every question. This means that when you add one question, you have to update all of that. What if you add 15 questions? Imagine the huge amount of code that that would take!  

So, time to fix that. All three of your functions do the same. They check an element for a specific value. They all get triggered on a keydown. Lets try to fix that to a single function:

// First select the elements we want to check the values of, you've allready classed those [fillBlank]:
$('.fillBlank').on('keydown', function(e){
    // At this point we have all the inputs on all keydown event, we only want enter:
    if (e.keyCode === 13) {
        // Now we have all the elements but only execute this on enter.
    }
});


Now comes the fun part. We want to be able to check ALL the inputs in one go, but give every input a UNIQUE value to check. For this we can use objects:

var correctAnswers = {
    one   : 'while',
    two   : 'on',
    three : 'occasion'
}
$('.fillBlank').on('keydown', function(e){ /* ... */ });


Neat little list like that right? Easy to expand aswell, just add one line et voila. We're now gonna add this to our code:

if (e.keyCode === 13) {
    // Now we have all the elements but only excecute this on enter.
    // Start checking the value for the input where the user pressed enter:
    // We can access the value via this.id because we named the input 'one', and there is a key 'one' in correctAnswers
    this.style.color = this.value=== correctAnswers[this.id] ? "green" : "red";
}


Well, thats it really. Now you can add plenty more items without building a million functions. The code below does the same thing as yours, but without hardcoding.

Result:

$("#vancouver").ready(function() {
    $(".fillBlank").val("");
});
// The correct answers:
var correctAnswers = {
    one   : 'while',
    two   : 'on',
    three : 'occasion'
}
// First select the elements we want to check the values of
$('.fillBlank').on('keydown', function(e){
    // At this point we have all the inputs on all keydown event, we only want enter:
    if (e.keyCode === 13) {
        this.style.color = this.value=== correctAnswers[this.id] ? "green" : "red";
    }
});




There are some extra things you can do to improve your code.


What if I type While. If you want to ignore uppercase, you can lowercase the this.value to always check the answers lowercased
You might want to add a check if this.id is an existing value of correctAnswers (hint: it's called .indexOf())
You might want to add/remove a class. CSS is for styling, not JS. This way, when you want to change the style of something correct/incorrect you do it in the stylesheet.
You might want to add the color names (or if you've updated the classnames) to a variable, e.g.: var outcomes = {right:'green', wrong: 'red'}; alert(outcomes.right);