Does the texture or shape hold special meaning?
I imagine hoding a model car in your hands is like "zooming out" for a blind person, enabling a contextual perspective that they cant get when interacting with the real world thing.
I imagine that scaling up to a whole new understanding of the world. Imagine the first lego set of the space shuttle a blind space enthusiast builds, and the immense set of knowledge that they cant otherwise get.
What a great idea to make this easier for them!
I'm not sure this directly answers your question. But I'm totally blind and my first ~7 years of education were spent at a school for blind and visually impaired kids. A whole lot of work goes into mobility training for children with disabilities, so for me it was how to hold and use a white cane effectively, how to navigate around unfamiliar environments, plan routes from A to B, etc.
I credit my first mobility teacher with giving me a life-long confidence in this area, primarily because he made super detailed lego models of the school buildings and used them to teach. I would have to carry out tasks such as moving my finger from a classroom in one building to the library in another via a valid, eficient route, and placing scraps of material in the right sections of the model based on my knowledge of the flooring materials used throughout the school.
It was so effective because it separated the learning of criticle skills from the pressure to perform. Getting up, walking around and demonstrating what you're learning was important, but it came with other responsibilities such as lookking after your safety. That could easily distract you from learning about acknowledging markers, developing a sense of direction and so on.
As an adult, I derive similar pleasure from woodworking and other crafts, but it's challenging enough to do that as a normal kid, to say nothing of also contending with folks who can't/don't support you because they don't know how or are too afraid. So, in the end, you have either legos or the simplest snap-together models to satisfy your building urge.
Even as an adult, I have a soft spot in my heart for legos. I've considered using them as snap-together cases for custom electronics projects, but haven't delved into them enough to know what sets would work best for that application. And as much as I like them, I really don't want to buy some castle or spaceship set just to build custom cases for my DIY doorbell or assorted RPIs. :)
You can then have them export the element list and you can buy the individual elements from the seller or sellers of your choice on https://www.bricklink.com on the secondary market and then you don't need to buy an entire set.
You could also just have someone sit down and help you buy a bunch of common elements in common colors from one or more of the larger sellers so you can have a nice little inventory of pieces.
Modified elements would probably need to be fairly descriptive:
- "place the 1x2 with the cylindrical protrusion"
- "place the 1x2 with the cylindrical depression".
- "place the 1x2 so that the rectangular textured masonry surface is facing out"
Anyhow, only noted because I encounter that sentiment often enough to call it out. "You're blind, so obviously you don't care if you get the garrish hot purple cell phone, if you've got the laptop with the cracked screen, ..." :P
Even in the early nineties when my mother worked with a blind man I found the limited technological aids at the time quite interesting but haven't a clue what variety of output devices might exist now and even things like cooking, where visual queues can often be quite helpful in determining if something is done such as "cook until golden brown".
And things like media, what sort of descriptive content is out there. I remember reading an article that talked about porn hub having descriptive content, but what sort of stuff is out there as far as streaming sites, what might various industry think about adding etc.
I know more exotic and niche thing like MUDs, multi-user dungeons, have actually seen a lot of blind-friendly adaptations in recent years, but what about other things. It would be neat to, pardon the expression, peek into the day in the life of a blind tech person.
However, an easy way to split by color would be to package bricks in different bags - as said bags have various shapes and textures as well. 
Granted, I'd love a solution that doesn't require sighted help. For this case, some sort of color identifier app might help. Given that Lego's color palet probably doesn't span too widely, this would probably be an easy weekend project.
The current lego pallet should still be at 51 colors, there might be issue with clear elements but for the most part they'll be significantly different than the other elements in a set being things like windows, windshields and cockpits. Also in a given set you are unlikely to have many, if any, of the same elements in similar shades that might get confused by an app.
The app would be useful for those that can see too just for listing elements on secondary markets like Brick Link.
It is far beyond my means but as an adult fan of lego I definitely see value in it.