Having worked with a multiple large corporations, and startups alike, I am noticing a common problem of missing persona's during project planning. Even being apart of 'collaborative' efforts with external UX Design firms... I am still seeing this problem.
So what's missing?
The incredibly important persona's that I can't seem to find in nearly any companies work... is those persona's with accessibility issues. Yep, you should be clearly, and early defining your users, that have colorblindness/visually impaired, blind, deaf, and deafblind users.
These users often depend on applications, computers, and technology more than non-impaired users. There is about 20 million visually impaired people in the United States alone, and that does not include deaf, or deafblind people.
This is a huge chunk of our population (10% of males, 1% females) , so why are we not including these people in our user personas?
Get yourself off to the right path next time you start a project... plan for those with accessibility issues early, and it will save time and effort down the road.