I'm experimenting with themes myself (I'm no expert) - this is just what I did - try it if you like.
As kyphi has said, it's a good idea to work on a copy of the theme ...
Go to /home/your-user-name/.themes (click View > Show hidden files)
Click Ambiance Minty folder
Click Edit > Copy
Click Edit > Paste
Rename copy Ambiance-Minty-2
Open Ambiance-Minty-2 > cinnamon > cinnamon.css
Scroll down the file a little way to the section
Code: Select all
box-shadow: inset 0px 1px 3px 0px rgba(0,0,0,0.3);
border: 1px solid rgba(95,110,75,0.2);
Those are the colors you want to change throughout the file
(light orange color)
(darker orange color)
I changed it to blue, so used
#648fb3 for the lighter color
#446bae for the darker color
(Of course, change these to your choice.)
Click Search > Replace
In Search for: field, enter
In Replace with:
Click Replace All
Do the same for the next color:
Search for: #ea703f
Replace with: #446bae
Click Replace All
Save the file > Close
Go to System Settings > Themes > choose Ambiance-Minty-2 > Apply theme
This should replace most of the orange color you wanted to replace in the theme.
It doesn't change the color of the hot corner "ripple" or of the arrows (when you hover on them) in the calendar.
If you wanted to go further and change them, you would have to edit the image files in ~/.themes/Ambiance-Minty-2/cinnamon, in gimp.
Again, this is what I did - there may well be an easier way
> Open with GIMP Image Editor
Render Scalable Vector Graphics window opens, just click ok (don't know why this happens - it's a .png file ?, but anyway ...)
In the menubar, click Colors > Colourise ...
For my example, I moved the Hue slider from 180 to 209
Click File > Overwrite corner-ripple-ltr.png > Close the file > click Close without Saving
Do the same steps for other image - corner-ripple-rtl.png
Restart cinnamon (press Alt+F2, press r, press enter) or logout/in to see the change in hot corner.
For the arrows in the calendar (hover), so you also need to do similar for the images:
> click Open with > GIMP Image Editor
(note: these files should open with the Render Scalable Vector Graphics window as they are .svg files but they don't ????)
Again, click Colors > Colorise ... change Hue to 209
This time (because GIMP can't save .svg files you need to do a workaround) -
click File > Export to (should already be in folder ~/.themes/Ambiance-Minty-2/cinnamon)
in Name: change end of name from .svg to .png so it reads
click Export > again click Export
click Close > click Close without saving
Do the same steps with image: calendar-arrow-right-hover.svg
Go back to ~/.themes/Ambiance-Minty-2/cinnamon
Rename the images:
It's a messy workaround, but the image names have to correspond to what's in the file cinnamon.css.
Restart cinnamon to see the changes.
If there are any more colors you want to change - you'll have to find and alter them similarly - that's all I changed.
EDIT: Note that the above is specific to the Ambiance Minty theme - other themes may be different.