I will vary the outfits based on more casual or formal settings. I try to keep the colors similar though because I have my characters color coded including their speech bubbles so that they stick out in my reader’s memories. That way when they see the character who wears a blue shirt and has blue speech bubbles it’s obvious who the character is and who is saying what. This is a trick I took from BL comic creator Sakurada Yana.
In Aoihito I vary character's outfit. They have their iconic piece of clothing, but they wear different stuff. On one hand this is good, because I don't have to draw them in the same outfit all the time if it annoys me, but on the other hand I have to come up with new outfits ideas. 
In TMoN characters are in a situation where they cannot really change their clothes. I made their clothing layered, so they can take one piece off when they need it. So far it made me realize I'm never making a character that wears long coat ever again. xD
I mostly draw them in their same outfits, but in the latest part they go to another world with a different ecosystem and they have to use special suits, so the costume change was part of the plot.
For the most part mine wear the same outfits (a couple of the MCs wears in layers so there are slight changes at points), but only because realistically thats the only clothes they own in their current situation.
However there will be points in the story where their outfits start changing a bit as a form of character development.
I also find it fun to see them in different outfits so yeah loool
My characters have default outfits that they wear 90% of the story, but sometimes I might have them wear something different. I mostly keep things the same since it's easier for myself and the readers.
For one of my chapters, the lead had to wear a different outfit because she fell asleep in her usual day clothes and it'd be weird for her to wear them to school the next day or have multiple copies of the same outfit.
I like to vary my character's outfits here and there. I think it helps keep their image fresh and interesting, not only for the reader, but for me to draw as well.
I treat my characters like cartoons characters; the ever lasting same outfit. It makes drawing easier, and I figure when the story progresses they can at least get a shirt change.
I write a novel so it's a bit easier, but I do aim for drawing my characters in different outfits. It's kind of fun to try and write more outfits for them, and then draw them. Or draw them in outfits that look like something they'd wear, but isn't.
I gave them different outfits for each chapter, mainly to show the events don't happen on the same day.
Plus, it's quite fun designing outfits.
my comic takes place in very early medieval times, so it doesn't make sense for my charactered to have a huge wardrobe. They sometimes change outfits, but only if it works in the plot! And sometimes they to things like, put on/take off capes and other accessories depending on what I feel like drawing, lol.
I try to evolve my outfits over time. After a big fight is a good time to get them a change of clothing as my poor guy and girl tend to get a little ripped up.
Eventually there will be a big fight with a scaly monster that will grant them a nice armor upgrade.
I pretty much do both; by having my characters where the same outfits, it keeps me in my comfort zone and stay more consistent, but by having them wear different outfits time to time, it get me out of my comfort zone and run my creativity. Plus, see how well I can get with clothes.
Plus, I do tend to wear the same outfit XD, so there is some connection there.
Oh I definitely intend to have my characters change clothes. However it'll be after each arc. So there's been one change from the beginning of the story til now.
I don't like seeing characters wear the same thing over and over. Unless it's a trait of theirs, or they're working on a job that requires a uniform.
For me, it depends on the character and the situation. A lot of the characters have uniforms so those typically stay the same. I change the outfits frequently on the main character Maddie because I feel it highlights her personality and wealthy lifestyle. On my characters that wear suits, I might change details like the color of the collared shirt or tie. I think a certain level of consistency helps the reader remember who is who, but switching it up keeps it more realistic and can reveal personality traits! i.e. I don't think one of my characters would wear a suit when taking his daughter to tumbling time, but he would definitely wear a suit at work to remain professional.
There are also situations where characters in suits might take off their blazer, untie their tie, or unbutton some of the top buttons of their shirts. I don't know if that counts as varying the outfits, but I think it helps illustrate how they're feeling at the moment.
Unless I have a very good reason for it, I always like to draw my characters in different outfits. Not only does it help reinforce the passage of time from one scene to another, but I feel like clothing really says a lot about a character's personality, and it can tell you a bit about the character just in how they dress and how they change things up. Plus I really like designing fun outfits for all my characters to wear!
