1/2 Deposit Returned Due to Horrible Paint Job

My question involves a security deposit in the State of: Maryland

For the first time I'm having legal issues with tenants over security deposit. The current tenants painted the master bedroom an yellowy orange, splattered marks were on the ceiling and on the chair rail. Initially I said they could paint but it had to be a neutral color. They told me that the color(it was already on the wall) was neutral according to a store rep. So me being nice and naive believed them. When they moved out I told them to paint over the orange splotches that was on the ceiling. they used a bright white color on a creamy off white color. It's obvious that it is 3 different colors in that room now. It was done very sloppily. I don't know if I am entitled to the half the deposit. I had a contractor come by for something and noticed it. So i asked him for a quote it was almost half the deposit. He said it was a day and a half job because orange, yellow and red are a painter's nightmare exact quote. it takes several coats to get rid of it. He also has to hand paint the chair rail to get rid of the orange splatters.
Before all this went down, I had to head to TX for the weekend, so I left my dad to do an inspection and get the keys returned. I gave the tenants a check for half the deposit in good faith. When I returned I noticed all this. I told this to the tenants(gave them the estimate of 575+materials) they are now being nasty and saying that my house was dirty and they want to seek legal action.
Do I have any legal standing to keep half the deposit?

Thanks!

You will be taking the position that the paint job constitutes damage to the apartment, not regular maintenance, as the color was not as authorized, the work quality was poor, and those factors significantly increased the cost of repainting.

If you normally repaint apartments when a tenant moves, your damages would be the increase in the cost of painting due to their use of yellow and orange paind and their unskilled work. Otherwise, you would apply the depreciated value based upon your typical repainting schedule.

Make sure you keep all of your receipts in case they sue you, and comply to the letter with your state's security deposit law.