Problem with colors on Illustrator

[Luigi 5E15]

Hi! I have an issue with colors (I'm new at illustrator..).
When I choose one color the result it's different from what I expected. I chose bright colors but in output they're not. Funny thing is that if I put in there a code and then I reopen the same level, the color code it's different from what I chose.
I'm sorry I can't explain better 😕

Do anyone knows which one is the problem and how to fix it?

Thank you in advance

[Doug A Roberts]

What is your document colour mode?

[Luigi 5E15]

Was CMYK.. I changed the colour mode of the image but not of the document. Thanks!

[Anna Lander · Accepted solution]

Check your document color mode. If it's set as CMYK, you see a closest printable color (the sample is under "Attention!" sign next to the color sample rectangle)
To have colors in artwork matched to the picked color, change the Document mode to RGB.
NB! If you print the artwork, the colors brughtness will decrease like you see now.