I doubt there would be any damage to the Pistol if an S&W .40 were accidently fired in it...the Bullet of the .40 would never even contact the Rifeling and or would be expelled without the Charge even reaching full pressure...and the Cartridge Case would likely never even expand enough to seal off the Breech.
I would be surprised that a .40 would even fire in a .45 given the smaller diameter of the Rimless Cartridge Case.
The 40S&W will load and feed from a 45ACP magazine into a 1911 chambered for .45 and will fire. The case will blow out and conform to the chambers diameter. There is a noticeable reduction of sound and recoil and usually a failure to extract. Similar results occur when a 9mm is loaded into a 40S&W. I have the casing for display when when I demo safe gun handling making the point that paying attention is a must.
The SP50204 spring for a 10 mm is listed by Brownell's as a Colt spring rated at 16#. The same as the standard spring for a 1911. I would think it would be rated higher
This thread talked about exactly what would happen when something like this occurs. I am guessing this is not a "what if" but an "I already did this is something broken" question? I'm with Oyeboten. No damage probably occured. Wolff Springs can also lead you in the right direction, or call Colt and ask them what spring setup they used.