PDF in RGB an CMYK

Is there another way for exporting in the RIGHT RGB color than creating a seperate document? 

No. Your two colors are not in the same color gamut so they can never match in appearance. If you choose colors that are in both the RGB and CMYK destination spaces, then you can work with CMYK color and get the same appearance by exporting two PDFs to the RGB and CMYK destinations.

If you don‘t care that the exported color appearance will be different—you want to preserve the out-of-gamut RGB color for the screen version—you can define the swatch color as 0/157/234 RGB, and let a color managed conversion happen on export by choosing the correct CMYK profile as the export Destination, which will output the nearest CMYK value for the device. The conversion of RGB color is always color managed and you can‘t force the conversion to a specific CMYK build.

You could file a feature request, but I don‘t think it is going to happen. The Adobe color management system, which handles all color conversions has been in place for almost 20 years.

Look into lab color.

Tragically, you might really like an RGB color but find yourself completely unable to print it.

The RGB color space has a much broader range of shades than conventional CMYK color printing. Loading your values into the Adobe Photoshop color picker shows how much your RGB color build is off from what you can actually print with standard CMYK printing on coated stock (Photoshop's default color setting):

If you were printing to, say, newsprint, the gap between what you see and want and what you'd get would be even larger.

In CMYK terms, your closest color equivalent will appear a little darker and duller than the RGB build. Taking Web Safe color into account, the color becomes even brighter onscreen, but not quite as light.

Looking at the same RGB color build within InDesign's New Swatch panel shows much the same information, but not as clearly:

You can see from above that the color is out of gamut, while the BinHex box at the bottom of the panel which reports the color shows non-web safe values, but you'd have to understand that color model to recognize that.

The short story is that you probably aren't going to get that color in print without mixing a custom color ink and laying that down as a spot color. No matter what kind of cool RGB swatch you'd see onscreen. In short, you may not be happy with the truth of what InDesign (and in this case, also Photoshop — which is a great tool for discerning specific color information) is reporting to you. But it is the truth, and it isn't lying to you.

Note that some colours, particularly bright greens and bright oranges, can't be reproduced in CMYK so for these, if you want them, you'll need spot colours.

Keep your images in RGB and soft proof to see how they will look in CMYK.

Select PDF/X-4 to supply your printer for converting to CMYK (unless they ask for another spec).