hii this is probably a very stupid question, but how do i get my name colorful like this person?

i know you have to use a color code thing, so i tried [ff0000], a red color like this person has, but it doesnt look colorful it looks dark

ive seen people use bright colorful purple, and light pink, but it doesnt work for me. when i try light pink i cant hardly see the color at all ;_; help would really be appreciated, thank u !!