Comment 9 for bug 1301607

I have confirmed this in the default Ambiance theme, and have included a fix for anybody interested which has been tested thoroughly on my system:

Before doing anything, if you are currently using Ambiance and it is your active theme, please switch to another theme such as default Radiance. Right-click on your desktop & choose "Change Desktop Background" from the menu, then under "Theme" option use the combobox menu to select Radiance; close the window & now we can proceed.

Open a terminal and type: sudo gedit /usr/share/themes/Ambiance/gtk-3.0/gtk-widgets.css; then input your password at the prompt and the default text editor should open with the defined widget styles for Ambiance ready to be edited. We are going to make a few changes to this file:

(1) You will notice when scrolling through this file it is fairly well organized with widget names for each type of Gtk3 object that is styled. You will want to find the "menu" style heading; in my customized css file it is around line 895. Scroll down just before the"context-menu" style declaration (line 976) and add these lines to fix the arrow button color while scrolling in large menus:

.toolbar .menu.button:hover,
.toolbar .menu.button:active,
.toolbar .menu.button:active:insensitive,
.toolbar .menu.button:insensitive,
.toolbar .menu.button,
GtkComboBox .menu.button:hover,
GtkComboBox .menu.button:active,
GtkComboBox .menu.button:active:insensitive,
GtkComboBox .menu.button:insensitive,
GtkComboBox .menu.button {
    color: @fg_color;
    background-color: shade (@bg_color, 1.08);
    background-image: none;
    border-style: none;
    border-width: 1px;
}

(2) Now go down to the "menuitem" style declarations at line 1018; scroll down a little further and you will see a style fix for lp:949368 identified as a workaround for earlier versions of Gnome. This fix is no longer needed with the default gnome 3.10 libraries included in Ubuntu 14.04; and in fact it is the cause of the problem. Simply comment out that workaround or delete it, it is your choice.

Now save your changes, exit the application, and change your theme back to Ambiance to see the results. I suggest you open Calculator click on the "Degrees" combobox and go down to "currency" and a long menu will open with the proper scroll-arrow buttons to confirm.