In the CMYK colour system the RAL 5012 is composed by combining four primary tones of pigment. To achieve this exclusive "light blue" colour tone, out of 100% maximum colour components, 75% cyan, 30% magenta, none yellow and 10% key (black) are used.
You can immediately see this result on this computer simulated CMYK diagram.
The mixture of these primary colours blends in the middle on a square space where all four different colour hue sheets overlap.

The conversion of RAL 5012 into RGB colour space requres specific composition of red, green, and blue primary colours. To construct hue matching "light blue" colour from the RAL chart as close as possible, we use the following values ranging from 0 to 255 on the RGB colour system: none of red, 137 green and 182 blue.
The three circle RGB diagram here provides illustrative example showing how blue value stands out clearly in comparison to red and green to construct this unique tone of colour. The RAL colour equivalent emerges in the very center, where all three primary colour circles overlap and combine.