Don't use Magic Numbers

AnkerConfigDialog
```
void AnkerConfigDlg::resetPresetComBoxHighlight() {
if (m_printerPresetsChoice) {
m_printerPresetsChoice->setColor(wxColour("#434447"),
wxColour("#3A3B3F"));
```

Those numbers should be defined somewhere so that if you change them in one place, they change everywhere. A typo in any file will mess up your colors.

Start at AnkerConfigDlg::resetPresetComBoxHighlight and search the project for the two color literals shown in the issue. Identify where the repeated color values are used, then verify that changing each shared definition updates all corresponding uses without changing the intended colors.

Written by the indexing model from the issue text.