InDesign is unusual because it can support two color modes (RGB and CMYK) in the same document.
However, when you make any object transparent, the same color space needs to be selected to be able to render the transparency correctly. This is controlled by the Edit > Transparency Blend Space setting. In a CMYK document, this is normally set to CMYK. So your RGB values are converting to CMYK.
It's normal that if you picked an RGB color it would display brighter colors because it has a large color space (gamut) than CMYK.
How are you planning on printing your document? What kind of printer?
Well yes, but the thing i want to achieve is, that it wont change the actual value of my color.
This was no problem until today, which i find weird?
I normally just print on a canon ipf6400
If you don't want to see transparent objects in the document's CMYK space set your Transparency Blend Space to RGB and turn off Overprint and Separation Preview. But that won't improve the conversion into the gamut, which is still going to happen at output.
Okay, but that still doesn't give me the result that I had earlier today (before the change).
I made at quick screen dump to show you.
Currently I have tried to set the green square to RGB(0,255,0) (no. 2 on the pic), but when I look at the square, and also when I reopen the color picker, the color er set to RGB(101,179,46) (no. 1 on the pic).
But if you look at the picture of the color spectrum it shows the neon/lime green nicely. Why can't I get the square (or any object for that matter) to do the same thing again?
Also if you are making colors from the color picker the color or swatch you'll get depends on where your cursor is in the picker.
So this will make an RGB swatch because my cursor is in an R,G, or B field (Add RGB Swatch):
And this will make a CMYK Swatch (54|0|69|0). The capture isn't showing it but my cursor is in the C field, which changes the dialog to Add CMYK Swatch
Thank you so much! that was the solution.
Probably just the cursor in the wrong field.