It says my federal return is 799 in green but the total I would receive is 143 in gray color

Then you must be seeing a state tax due---Look at your actual tax returns if you do not understand the summary on the screen.  Federal refunds are on line 20 of your Form 1040; federal tax owed is on line 23 of that form.

Every state form is different so we cannot tell you what line to look at on your state form, but if you look it over carefully you should see it.  Does it show a refund or tax due?

You must pay your state tax due using the state’s preferred method of receiving payment.  For most states that will be by making a payment to the state’s own tax website, or by mailing a check or money order.

https://ttlc.intuit.com/questions/1900884-what-are-my-options-for-getting-my-state-refund-or-for-paying-any-state-taxes-i-owe

Some states are giving extra time to pay 2019 state tax due.  For the most up to date information about your own state—go to the website for your state:

https://ttlc.intuit.com/questions/1901670-how-do-i-contact-my-state-department-of-revenue