The chemical test used by law enforcement agencies to estimate a person`s blood alcohol level involves a reaction with ethanol. In this test, the person blows into a bag containing a solution of sodium dichromate in an acidic medium. The reaction between ethanol and the sodium dichromate solution causes a change in the color of the solution.

Option 1 states that the color of the solution changes from orange to green. This is the correct answer. When ethanol reacts with the sodium dichromate solution, it reduces the dichromate ion to chromium ion. This reduction reaction causes the solution to change from its original orange color to a green color.

Option 2 states that the color changes from orange to colorless. This is incorrect. The solution does change color, but it does not become colorless.

Option 3 states that the color changes from yellow to orange. This is also incorrect. The original color of the solution is orange, not yellow.

Option 4 states that the color changes from colorless to orange. This is incorrect as well. The solution does not start off as colorless.

In conclusion, the correct answer is option 1, where the color of the sodium dichromate solution changes from orange to green when reacting with ethanol.