In the Microarray Shown in Your Textbook, the CDNAs Were

In the microarray shown in your textbook, the cDNAs were labelled with red and green fluorescent tags. How then do you end up with spots on the microarray emitting yellow light?

A) In light, red and green are two of the primary colours, and the combination of the two will produce yellow light.
B) The yellow light comes from the laser, and a yellow spot indicates that neither cDNA hybridized to that spot on the microarray.
C) The over expression of one cDNA relative to the other will skew the colour pattern of the spot on the microarray. This results in the yellow colour.
D) The colour choice was an arbitrary decision by the artist and doesn't reflect how the process actually works.