Do eyes accommodate to color?
I don't think it is a matter of color/hue. Do you have a source for this hypothesis? If you were able to measure this effect then I would think it happens because of the importance rating a reader develops for a certain group of highlighted words, e.g. "all blue highlighted words are important to me."

The user Pete made a good comment in my opinion by pointing out the contrast issue. The attention of humans is foremost guided by luminance contrast. Then comes hue and then saturation. The colors you chose have a different luminance value and therefore attract attention differently.

Here's a link to compare the (relative) luminance values of your color sets.