Hey there,

To add styling modifications to your report tables, you'll have to add the specifications over in the table class while designing the report.

Let's say, you're designing a report with a table in the studio mode. 
Step - 1 : Click on "Edit sources" to find the qweb layout code
Step - 2 : Click on the table in your report to navigate over to the table class in your code.
Step - 3 : Add styling options to your table class. To eg, if you want to have a table with background colour as green, text in white and red border you'll have to specify it as -

<table class="table table-bordered" style="background-color:green; color:white; border-color:red;">

and 

<td style="background-color:green; color:white;">

Step - 4 Click save for changes to be applied to table. 
Hope it helps!

odoo guide is available to style your pdf Reports

check this out :)

http://odoo.guide/?s=report 

Hi Chandi

       You can make use of all available table defined in the bootstrap.css

        If you want to use your own design , it is possible by defining the css inside the style tag of you template

        For example

<template id="student_test_report">

 <style type="text/css">

 .bb {

 font-weight: bold;

 }

 .brr{

 border: 5px solid green;

 }

 .tbt{

 border-top: 2px;

 border-color: black;

 border-width: thick;

 }

 </style>

.....

.....

.....

</template>

I think this will help you.