Pb with the color of the header when creating a sub-theme of Garland in sites/all/themes

Needing a very slight change in the CSS of Garland Theme, I created a Sub-theme of Garland, following the example of Minelli, but I put it in the sites/all/themes directory. I changed the relative file paths in the color.inc file, accordingly, as shown in the attached file. All seems to work fine but when I change the default color to "shiny tomato", for ex., the color of the header remains blue, while all the rest follows the "shiny tomato" color settings. I, then, tried to define the same sub-theme but, in the themes/garland directory, with the same color.inc as the one in the Minelli directory, and all was fine. It looks like a bug ... Is it ?