There are many professional photo websites on the Internet, but it's not bad to deal with them with photoshop. There are many video tutorials in Photoshop, just look at Baidu.

There are many ways to adjust colors, such as color balance, color scale, etc. , but there are only a few parameters, and you will know after playing a few times.

Besides, the background is all white, so I'm not sure what you mean. According to my understanding, is it just a flash? However, if there are only people and the background is invisible, it also involves masking. If you are careful, you may need to pave the way. If your wedding video is mixed color and has many moving shots, it will be more troublesome to follow, and the effect you said is more difficult to achieve.

Good luck.

At 3 minutes and 32 seconds, don't draw directly with the mask of AE itself, because it looks too soft. The person who made the video should have made an alpha channel in ps in advance, with a gradient, and then imported it into the mask made by AE.

There may be a particle effect in 38.39 seconds. This is just a guess. I'm not sure, but it must be a single effect, moving with the key frame.