Many bloggers are facing issues while uploading photos on blogger like loss of picture quality, change in colours etc. This is because Blogger is connected to Google+. All the photos you upload to blogger is going straight to your Google+ account.
In Google+ there is an option to enhance photos automatically. This is actually causing this problem. So you have to disable this feature.
To disable Auto Enhancing Follow These Steps.
Step 1: Login to your Google+ account.
Step 2: Go to this link.
Step 3: Scroll down and find 'Auto Enhance' option.
Step 4: Turn off this feature.