I would think that rather than compounding a mess by asking strangers here who will have many ideas, you'd be best to ask some experts, at least the senior people at places like Home Depot, etc.

You can't remove it and even if you applied different colors you may never be happy with the results. Most likely it's the way the concrete absorbed the stain that is causing the streaky look and not the way your DH applied it.

Call your local masonry/concrete business and explain your problem. They should be able to give you some names of companies that can help you. Otherwise, google 'staining concrete (along with your city & state)' and see what pops up in your area.

This is an all too common problem. BAD stained concrete job. It's tedious work that MUST be done by an experienced contractor - usually with TWO people. The surface must be prepped and the post-stain cleaning and sealing must be done right. I just ran into this with Kemiko in New York. The installer was TOTALLY unqualified (didn't know until after). They brought in some Slick Regional Salesman to BS me about how all of the streaks, drips, missed areas and ghastly aberations were "totally normal". I've seen competent jobs and KNOW this is not the case. Nevertheless, they'll likely all protect each other and try to get you to back down saying it's the "unpredictable nature of the concrete". Argh... what can you do? You can grind off the top later of concrete, but this will likely expose more aggregate that's below the surface and give you a different concrete look. You can essentially "paint" over it with an opaque water based stain. Bottom line is that you got taken by a contractor who was over his head and will not make it right. Join the club...there are thousands of us out there.

Don't cry, you do have options.

There is an epoxy based product that you could coat the concrete with that looks very nice. But, before you go through that effort, have someone look at it to see if a good etching and reapplication might help. As mentioned before, you could also paint it but that requires good preparation also and it will become an ongoing maintenance issue. He could also apply several applications of his stain, going in different directions until it looks more presentable. That could give it a linen look.

I'd call a professional. Stains can be tricky, especially if your husband already sealed it. You might have to grind it up too. From what I've seen, I think having a professional come out and stain your patio is around $2.50 a square foot.

Here is a link that might be useful: Concrete Stain Info

You might search (and post) over at This Old House. There are a lot of experts over there. Although it seems there are already a couple in this thread saying it's going to be tough to get that off!