It depends. Would your husband use it while traveling a lot or will it be mainly used in a home/office etc where Wi-Fi is available? If it's going to be used while traveling then it might be worth looking at a 3G model note that your husband would have to pay for a data contract for this or get a pre paid data sim card.
Storage it depends on the person really and if they are going to load it up with lots of content such as Movies, TV Shows, Music, Apps.
I would say if it is mainly going to be used for apps and not lots of video content etc then 16GB should be enough for that but I would say that 32GB is the best option as at least with 32GB you may have more storage than you need but it's better to have too much storage than be wishing you had more.
64GB should only really be considered if you are a heavy content consumer with many Movies,TV Shows, Music etc loaded on the device in my opinion.
As for colour well that's personal preference.