She is 3 1/2 and when she askes why it’s even after you answer it but then she says why that color is red mostly about everything is but why... could their be something g wrong
This is absolutely normal. At that age children want to know everything, and they don't yet have enough experience to help them understand "why" so you are their source of information. Everything they get is from you.
They may or may not even listen to your answer, to be honest, as communicating with you and having you respond with anything will please many children. I used to enjoy making up stories to answer questions like, "Why is the sky blue?" that may not have had anything to do with the truth... :-)
Don't worry about it, instead, use it as an opportunity to communicate, to bond, and to play with your child.
First off, its normal. Evidence: the picture below exists and causes knowing smirks and groans in parents.
As to why they ask why (oh gosh, why-ception is starting), the short answer is it is a magic word for more attention from mommy/daddy.
Remember, they are still learning to speak. And part of learning speech is hearing and repeating. And they heard you say it, so they try it out. And oh my gosh that got a lot of talking out of you. Which means attention and time with mom/dad. Hooray!
They haven't gone through enough trial and error with it to know what that "why" word really means. But they just know it gets you to keep talking, keep giving attention and they like it.
Eventually they figure out that "why" is how you ask for explanations about things, get insights into thought processes, etc. But for now, it's a magic word1 that means more attention. And that's enough for most toddlers.
1 Other magic toddler words that they just use without knowing what they mean to the rest of humanity include, but are not limited to: "no", "NO", "NOOOOOOOOOOOOOOOOOOO!!!!!!!!!!" and "potty" ("potty", "But this is your 73rd time before bed, you can't possible have anything left", "potty", "No, go to sleep", "POOOOOOTTTTTTYYYYYYYY", "Fine. Let's go." ":)").
"Why?" is in contention with "play with me" and "NO" for the most expected thing a comfortable three year old will say.
She has figured out that the most interesting things in her world are people. "Why", "Play" and "No" are words to conjure with, since they make adults pay attention and act in unexpected ways. If she didn't feel comfortable with her people and secure in her status she wouldn't use these attention attracting words. Of the three "Why" is least hassle, because most people can talk while continuing to do whatever.
It is a nice reminder that you have an opportunity to shape her mind. Almost certainly you know a lot of stories with a moral you approve of, this is the time to bring them out. A three year old isn't really expected to be able to hold onto the first why through even a short story, so you don't need to try too hard to stay on topic even.
"Why do cars have steering wheels?"
"Once upon a time cars had no steering wheels. One day a wolf and a dog met and started talking, the wolf said ...[story about sharing]"
If you don't have a stockpile of traditional stories you like at the tip of your tongue you can make your own; with a little practice extemporaneous shaggy dog stories staying vaguely on topic with anecdotes relatable to recent or major events in her life are not really that hard, and she probably won't be at all critical of your story telling abilities no matter how much you struggle at first.