Only problem with 445nm+ blues (unless low power single mode) is due to being multimode their divergence is relatively high compared to a DPSS 532nm green. Also, a relatively inexpensive 100mw 532nm green will be 10 times brighter to the eye than a blue or red laser due to the sensitivity of the eye to green which is much higher. Last but not least, 532nm DPSS green lasers are typically 1.2 to 1.5 mRad of divergence, high power red or blue multimode diode based lasers much higher, 1.8 mRad and up, depending upon the design, 2.5 mRad is not unusual for blue, up to 5 mRad for red.
If you want to use a high power blue, I recommend getting a 10X beam expander for it. Some manufacturers such as Jetlasers offer beam expanders for their lasers. This will reduce the divergence to be better than a 532nm DPSS green laser, but you will have a fainter beam, milliwatt to milliwatt compared to green. A way around that is to use a high power blue such as 2 watts output with a 10X expander. Of course, the blue 445nm high power lasers, as well as a 100mw laser, need to be handled with great care, both power levels are dangerous and can blind, the blue extremely efficiently.
In my opinion, best of all is pairing a 532nm DPSS laser with a 10X beam expander which are available from just a few milliwatts of power all the way up to about a watt. With a 532nm DPSS green lasers you are already starting out with a laser beam which is brighter to the eye than red or blue, lower divergence too which with a 10X expander, reduces it far below what you would get with a blue multimode diode laser even if it were using a 10X expander. The reason for this is if you start out with low divergence and use an expander, i.e. 10X, the divergence is reduced by about 10 times less, so starting out with a high amount of divergence, you get 1/10th with a 10X expander, sure, but it won't compete with a 532nm green laser which had a relatively low divergence to start out with.
If you are considering a 520nm green multimode diode based laser, they also have poor divergence without a beam expander, compared to DPSS 532nm green lasers, but due to green being far more visible to our eyes than blue, a good trade-off, but in my biased view, only if using a 3X or higher beam expander to put them close to what you could get with a 532nm DPSS laser. Put a 10X beam expander on a 1 watt 520nm green multimode diode laser and now you have something impressive, the beam might be 25mm thick, but it will go a long distance without much spread and at that much power, will light up the night sky with an impressive beam. Even a 100-150mw 520nm multimode diode laser with a 10X expander does a good job lighting up the darkness, nothing wrong with that.
One last word, your project won't work if using a multimode diode based laser at any color, unless using a good beam expander, the end of the beam from one of those just fans out and dilutes in a huge spread at two miles. I've tried to put a spot on a cloud at 6000 feet using a 2 watt blue 445nm multimode laser and couldn't do it, but I could with a 100mw 520nm green single mode laser (50mw laser diode being pushed to 100mw out) which did not require a beam expander due to single mode diodes having such low divergence, even better than some of the 532nm DPSS lasers. You might try a single mode 100mw output 520nm laser with a beam expander on it to make an even tighter spot, it will deliver FAR more power to a spot two miles away than a 2 watt blue multimode diode based laser.