First child not working

[ladybug]

So I have this code and all the headers are with gradient even though I specified only first child. The others should be green. When I try with another code it works,why doesn't with mine?

*{
	margin: 0px;
	padding: 0px;
}
header:first-child {
	background: rgb(255,0,0);
    background: linear-gradient(90deg, rgba(255,0,0,1) 0%,rgba(255,0,0,1) 33%, rgba(0,128,0,1) 33%,rgba(0,128,0,1) 66%, rgba(0,0,255,1) 		   66%,rgba(0,0,255,1) 99%);
    color: #ffff00;
    text-align: center;
    font-family: Arial;
    font-size: 35px;
    font-weight: bold;
    padding-bottom:15px;
    padding-top:1px;
}
header{
	background:green;
}

UPDATE:same with first-of-type

Edited April 30, 2021 by stefanmz
Update

[DPS100]

You might want to be more specific with your question and change your title to describe your problem a bit more, or add tags to get people who can help you interested (ex. I'm not sure what language this is written in).

[ladybug]

2 minutes ago, DPS100 said:

You might want to be more specific with your question and change your title to describe your problem a bit more, or add tags to get people who can help you interested (ex. I'm not sure what language this is written in).

Oh yeah sorry I forgot CSS but I actually solved it by just using the element in element structure like element element{code} you know 

[DPS100]

1 minute ago, stefanmz said:

Oh yeah sorry I forgot CSS but I actually solved it by just using the element in element structure like element element{code} you know 

I don't know CSS, but I'm glad to hear you figured it out! Sometimes just asking a question gets you in the mindset to solve it.