Nope, that’s common icon colours. If you want to customize the folder’s colours, see:
"sidebar_folder_icon_color": "$icon_color",
"sidebar_folder_icon_color_on_hover": "$icon_color_on_hover",
"sidebar_folder_icon_color_on_expanded": "$accent_color",
"sidebar_folder_icon_color_on_expanded_hover": "$accent_color",
"sidebar_folder_icon_color_on_selected": "$accent_color",
"sidebar_folder_symlink_icon_color": [
"specify",
["rgba", 255, 255, 255, 0.75],
["rgba", 0, 0, 0, 0.75]
],
"sidebar_folder_symlink_icon_color_on_hover": [
"specify",
["rgba", 0, 0, 0, 0.75],
["rgba", 255, 255, 255, 0.75]
],
"sidebar_folder_symlink_icon_color_on_selected": "$sidebar_folder_symlink_icon_color_on_hover",
"sidebar_folder_loading_icon_color": "$sidebar_folder_symlink_icon_color",
"sidebar_folder_loading_icon_color_on_hover": "$sidebar_folder_symlink_icon_color_on_hover",
"sidebar_folder_loading_icon_color_on_selected": "$sidebar_folder_symlink_icon_color_on_selected",