Howdy whitesalmon
Our friend AlohaBob asked me to have a look here - mainly about your inability to insert your iPhone photo of your Mac's Mail window.
I am a pretty good "searcher". That brag out of the way, I cannot find anything about your Mail "reddish hue" issue. My best guess is that is is simply an 'indicator' of your reported "on the server" status, but don't bet on my guess.
Apple's search is just "OK" - ASC search is terrible (two different things entirely - Support articles are actual files on a server's directory tree and ASC discussions are contained in a database)
I search using Google Site Search mostly, but I sometimes 'get lucky' searching Apple Support
Apple - Support - Search < this will require 'browsing the results'
https://www.google.com/?gws_rd=ssl#safe=off&q=mail+red+site:support.apple.com < mickey around with search terms, leaving ' site:support.apple.com ' alone - all the Google search modifiers are allowed = quotes, * for wildcard, Filter tools such as "Date", etc.
This should be very straightforward. I would be very interested in exactly what happens when you try to insert an image. A detailed description of every action you take and the results - step-by-step - will have to suffice, I guess - since the issue is NOT being able to post a screenshot!!
Sometimes, when I attempt to Drag & Drop an image from the Finder to this Reply window, the blinking "text cursor" - NOT the "I-bar" text select cursor, but the one that indicates WHERE the nest keystroke will be - "disappears" (this is apparently due to my fumble thumb and TrackPad accidentally "tapping" outside the textBox)
If you are NOT employing Drag & Drop, you must be using the camera tool of the TinyMCE editor. That process may give you error messages in the popOver Pane.
You can also use the Clipboard. To take a screenshot TO the Clipboard - simply add the "ctrl" key to the key combo you normally use then PASTE "CMD+V" where the blinking text cursor is
example = CMD + CONTROL + SHIFT > 4 = 'marquee cursor" selected area to Clipboard - THEN Paste

*I also replied to your other thread thinking it was a logged out by timeout or Glitch issue