Why not use whatever one suits your fancy at the time? Whatever makes you happy should be what goes, I think. And if you're the type that likes to change it up a lot, maybe your character likes to make temporary changes, too. Tattoos, dyes, etc.

this is actually a great idea. why shouldn't your character be able to add/cover markings with dyes or makeup? i'd never considered it before!

Ayyyyy.. I also like this idea! Thank you~

For markings changing, if small change, you could say they dye the fur. Think henna tattoos for furries!

I was the same with Sushi when I first made her, she was originally a natural Japanese Bobtail but I didn't like natural colors and opp'ed for the pastel blue. I also added the arm markings due to two things, I love pandas but didn't want a bear and my previous fursona to her had similar markings and I liked it. Recently I just changed her hair to the pastel purple, so I get where you come from when you say small change but big impact on how you like it!

Simply add "blue ring octopus hybrid" to your species and then you can change markings on the fly.

Many species naturally have changes in their fur based on the season, so if you wanted a naturalistic explanation for it you could use that. But also, I don't think there's anything wrong with just having alt-designs as long as the primary traits are still recognizable. Generally if the character has a strong sillouette/design the colors matter less. A good example of an artist who does this kind of thing with their characters is  ashiji so you might want to see how she handles changing color palettes!

The first comment suggestion is great! I also like to give it a grace period. Sometimes when I make something new I'm so excited and love it but when the excitement goes away sometimes I fall out of love. So if possible I leave it for a bit and go back and see which ones I still love.