You can use one command to press a key and another to release it, but you still need to pause at least once between them.
E.G. if you have a command with the phrase "gray" with the "Recognition" option set to "Restricted Continuous Speech", so that the command is recognized if you say "gray" and continue speaking without pausing afterward, you'll still need to pause before a second command can be recognized.
Note that a single word, especially a short one, is not recommended for use with the "Continuous Speech" options, as it's likely to recognized erroneously (you can try changing the "Minimum confidence level" option for that command, but you may not find a balance between reliable recognition when you speak the word intentionally, and erroneous recognition).
In addition, there is a recognition delay to any command, so if you say "gray" and continue speaking, the first part of whatever you say is likely to be inaudible.
As, logically, a command must be spoken before it can be recognized, "over" would also be heard at the opposite end.