Wrong.
The more to the left you go, the less penetrating power, but more ionizing the laser will become.
Any wavelength of a laser would be deadly if sufficient power is applied. If you have an X-ray Laser, for instance, it would... hmm... cauterize any organic matter you point your weapon at, or at lower power settings, produce cancers and damage DNA, or at even lower power settings--take a Rontgen picture of somebody. A microwave laser will be able to cook something inside of a power armour by boiling the water inside their body; at lower settings it will produce unpleasant effects like headache and such. However, neither of these lasers will be visible to our eyes, unless we have special mod installed to our power armour helmets that allows for us to see them. A blue laser and a red laser can be equally destructive, although the way they work are slightly different. Blue laser is more ionizing, meaning it will energize electrons, which, in turn, will leave their electron clouds from the atoms, thus producing a chemical reaction that damages the structure as a whole(generally applies to the shorter left spectrum.) Red lasers--generally speaking red light is the carrier of heat in nature, will incite whole atoms and make them vibrate more, tearing down the original structure(generally applies to the right longer spectrum.)
If you don't believe what I say, the simple proof is to look at the Sun very early in the morning and at high mid noon. In the morning the Sun is red, because the light from the Sun has to penetrate through more atmosphere because of the round shape of the Earth; only the red spectrum is able to reach our eyes. At noon the Sun appears near white, because it shines through a lot thinner layer of atmosphere, so more of the visible spectrum reaches our eyes and when the colours mix, you get white.