How to Customize Themes

You can make your blog stand out by playing around with blogger's numerous choices of themes. 

1. Sign in to Blogger.
   
   
2. In the top left, click the Down arrow .
   
   
3. Click a blog to update. 
4. In the left menu click Theme. 
   
   
5. Under “Live on Blog," click Customize.
6. Use the left menu to customize your background image or color and to adjust backround, 
   
   
   
   
   
   widths, 
   
   
   layout, and other settings. 
   
   To change the font and color follow these directions:
   
• In the top left corner, click Advanced.
  
• Choose the font, font size, and font color you want for each kind of text you want to use.
  

For the last step, in the top right corner, click Apply to Blog to make your changes live.

Reference Link: https://support.google.com/blogger/answer/1227173?hl=en&ref_topic=6321969