Not really. Although you can set the preferences to show many of the elements in red (Preferences>Display Colors) there are some that aren't available to the color selection. You might do better by saving your score as a PDF, and changing the colors in a graphics program.

Thank you Mike! I've just tried with Display Colours, and in fact, I can't change it for both clefs and time signatures. But then, when I try to export the score as graphics or print it as a PDF, colors do not show, they just chenge back to black.

I thought about doing it with a graphics program, but it impossible to keep the scores as a vector and it takes ages... maybe I should write in a InDesign or similar forums for this.

In your print dialogue, you should see an checkbox to “print display colors.” Check that, and see if it helps.

… I thought about doing it with a graphics program, but it impossible to keep the scores as a vector …

It sounds like you by your words “graphics program” mean a program that works on bitmap graphics (a. k. a. a painting program).

Instead, use a program that works on vector graphics (a. k. a. a drawing program), like e. g. Illustrator, or Inkscape.

Thank you Peter! I'll try with Illustrator.

And thank you again, Mike. Print colors is great!