Color change in beamer at R markdown

Question

Esteemed,

I'm having trouble putting together a beamer presentation. I would like to put the title, the footer and the items in green tones.

I appreciate any help.

title: "long title"
date: "10/10/2020"
output: 
  beamer_presentation:
    theme: "CambridgeUS"
    keep_tex: true
header-includes:
  - \AtBeginDocument{\title[short title]{"long title"}}
  - \AtBeginDocument{\author[author1; author2; author3; author4]{author1\\author2\\author3\\author4}}
  - \addtobeamertemplate{headline}{\includegraphics[width=\paperwidth,height=2cm,page=2]{img.png}}
 
---
# Introduction   

* text1;  

* text2;  
 
* text3;

* text4.