Bright sun today, Nikon P900, Bright colors of red, yellow, orange do not appear in pictures.
Wow. Read this with my morning coffee. Seemed to be an average "first post" by a newbie, looking for advice in a very general sort of way.
Come back at lunch and it's turned into a pissing contest between a virtual fire hydrant of venom, and a flood of those calling for respect, with a sprinkling of actual advice.
Here's mine, FWIW....
1) Always try to get some blue sky (or even a manmade object that's in the strong blue color range) for contrast into your photos. Fall colors don't really pop, to me, unless there is another splash of color from the opposite side of the color wheel. Some people are fine without it, but I think it makes the fall colors look stronger in a more natural way. Try a polarizer to enhance and darken the blue. Or try it selectively in post processing.
2) Try the Vivid color selection on your Nikon, and see if it makes a difference in your JPEGs. Some like the effect, but it's easy to overdo. I don't have a P900 but I've had other bridge cameras where this made a big improvement, others where it went crazy. I have used it on occasion on my DSLR Nikons when I wanted a quick image. If you do post processing, the color, saturation, vibrance, and luminance sliders are your friends, depending on what software you use. I guaranty the first shots you play with will be overdone a little.
3) Foliage looks best when lit from the side, overhead shots will often look a little washed out. Look for golden hour lighting in the morning or late afternoon instead of high noon.
4) Try underexposing by 1/3 to 1 full stop. You can also try this in post processing if you're unsure or don't have multiple exposures to play with.
5) Learn how to post images! It's pretty easy and it will cut the percentage of bad answers you receive.
6) It will take only a few posts for you to begin to separate those who want to offer advice and encouragement from those keyboard warriors who love to show off their alleged intellectual superiority by demeaning others. The former will jump right off the screen - but then you'll have to learn to sort the good advice from the bad! The latter need to have their mothers turn off the WiFi in the basement.
Don't let the grumpy old farts discourage you from asking newbie questions. The juice at UHH is worth the squeeze.