Before starting the third part I recommend that you please go through the previous parts on AngularJS Validation:
This part will teach you how to,
- Apply CSS to validation message
- Disable or enable the button depending on validation message
- Change the color of controls as per validation
Initial requirement is reference 
- <script src="~/Scripts/angular.js"></script>   
 
- Apply CSS to validation message 
 
 i. Below CSS will help you to apply css to the validation message,
 
- .ValidationMessage {  
- color: red;  
- font-size: x-small;  
- }  
 
 And to the control of message apply below way,
 
- <span class="ValidationMessage" ng-show="myForm.email.$dirty && myForm.email.$invalid">  
-                 <br />  
-                 <span ng-show="myForm.email.$error.required">Email is required.</span>  
-                 <span ng-show="myForm.email.$error.email">Invalid email address.</span>  
-             </span>  
 
 
 
- Disable or enable the save button depending on validation 
 
 By below way you can enable / disable the save button control on validation,
 
- <button ng-disabled="myForm.$invalid">Save</button>  
 
 
- Change the controls as per validation.
 
 For Invalid control CSS is,
 
- input.ng-invalid {  
- background-color: pink;  
- }  
 
 For valid control CSS is,
 
- input.ng-valid {  
- background-color: lightgreen;  
- }  
 
 
My final code will look like as below,
- <script src="~/Scripts/angular.js"></script>  
- <form ng-app="myApp" ng-controller="validateCtrl"  
-       name="myForm" novalidate style="width: 470px;margin: 0 auto;border:medium;margin-top:10%">  
-     <fieldset>  
-         <legend>Validation Demo</legend>  
-   
-         <p>  
-             Student Roll Number:<br>  
-             <input type="number" name="StudentRollNumber" ng-model="StudentRollNumber" required>  
-   
-             <span class="ValidationMessage" ng-show="myForm.StudentRollNumber.$dirty && myForm.StudentRollNumber.$invalid">  
-                 <br />  
-                 <span ng-show="myForm.StudentRollNumber.$error.required">Student Roll Number is required.</span>  
-                 <span ng-show="myForm.StudentRollNumber.$error.number">Not valid number!</span>  
-             </span>  
-         </p>  
-   
-   
-         <p>  
-             Student Name:<br>  
-             <input type="text" name="Student" ng-model="Student" required>  
-             <span class="ValidationMessage" ng-show="myForm.Student.$dirty && myForm.Student.$invalid">  
-                 <br />  
-                 <span ng-show="myForm.Student.$error.required">Student Name is required.</span>  
-             </span>  
-         </p>  
-   
-         <p>  
-             Student Birth Date:<br>  
-             <input type="date" name="BirthDate" ng-model="BirthDate" required placeholder="yyyy-MM-dd">  
-             <span class="ValidationMessage" ng-show="myForm.BirthDate.$dirty && myForm.BirthDate.$invalid">  
-                 <br />  
-                 <span ng-show="myForm.BirthDate.$error.required">Student Birth Date is required.</span>  
-                 <span ng-show="myForm.BirthDate.$error.date">Not a Valid Date.</span>  
-             </span>  
-         </p>  
-   
-   
-   
-         <p>  
-             Student Email:<br>  
-             <input type="email" name="email" ng-model="email" required>  
-             <span class="ValidationMessage" ng-show="myForm.email.$dirty && myForm.email.$invalid">  
-                 <br />  
-                 <span ng-show="myForm.email.$error.required">Email is required.</span>  
-                 <span ng-show="myForm.email.$error.email">Invalid email address.</span>  
-             </span>  
-         </p>  
-   
-   
-   
-         <p>  
-             Student Percentage Marks:<br>  
-             <input type="number" name="marks" ng-model="marks" max="100" required>  
-             <span class="ValidationMessage" ng-show="myForm.marks.$dirty && myForm.marks.$invalid">  
-                 <br />  
-                 <span ng-show="myForm.marks.$error.required">Email is required.</span>  
-                 <span ng-show="myForm.marks.$error.number">Invalid number.</span>  
-                 <span ng-show="myForm.marks.$error.max">Max Percentage is 100.</span>  
-             </span>  
-         </p>  
-   
-   
-         <br><br>  
-         <button ng-disabled="myForm.$invalid">Save</button>  
-   
-         <p>  
-     </fieldset>  
- </form>  
-   
- <script>  
-         var app = angular.module('myApp', []);  
-         app.controller('validateCtrl', function ($scope) {  
-             StudentRollNumber = 12;  
-             BirthDate = new Date(2013, 9, 22);  
-         });  
- </script>  
-   
- <style>  
-     input.ng-invalid {  
-         background-color: pink;  
-     }  
-   
-     input.ng-valid {  
-         background-color: lightgreen;  
-     }  
-   
-     form.ng-pristine {  
-         background-color: lightblue;  
-     }  
-   
-     .ValidationMessage {  
-         color: red;  
-         font-size: x-small;  
-     }  
- </style>  
 
Run your application you will find the error message working as below, 
- Invalid State : Check the CSS of message,
 ![Invalid State]() 
 
- Valid state control CSS will looks as below,
 
 ![valid]() 
 And in valid state Save button will get enabled.
So by this way you can apply the CSS , you can change the color of the control in invalid state as well as valid state and Enable or disable the control in valid state.
Read more articles on AngularJS:
 
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