This pdf is 13 pages long, 2/3 of a page front cover, 1 page editorial & SRD, leaving 11 1/3 pages of content for the mosaic mage, so let's check it out!
What are the Mosaic Mages? Essentially, they are a variant of the regular specialty wizard that gets access to a certain selection of sub-schools of wizardry as well as abilities based on the colors (or combination thereof) of their specialization. Fluff-wise, a magical tint may accompany them, infusing their very being with the color of their magic. Every 4th level, the mage gets a spectrum power.
Each of the primary spectrums the mosaic mage can choose has 2 subspectrums and preparing spells from these schools take up 2 slots instead of one. In addition to this, Mosaic Mages can e.g. specialize in mixed spectrums instead of the primary ones, choosing 5 of the 9 schools and sub-schools of the component spectrums, a green mosaic mage e.g. choosing from yellow and blue.
Each of the spectrums gets access to a kind of energy associated with the color (if you know the color-code of chromatic dragons, then you know what kind of energy the color gets access to) and depending on the color, other sub-schools. Unsurprisingly, e.g. Black gets access to Necromancy and Illusion (Shadow), Abjuration, Enchantment (Compulsion), Illusion (Phantasm) and Evocation spells with the [Acid]-descriptor, while Blue gains access to Illusion (Glamer), Abjuration, Conjuration (Teleportation), Divination (Scrying), Transmutation (Polymorph) and Evocation [Electricity]. In case you're wondering: Yellow gets [sonic]-spells, while white gets actually access to Conjuration (Creation) and Conjuration (Healing)-spells, making the mosaic mages a rather interesting choice in that the white mages may provide healing without being divine casters.
Each of the spectrums gains access to a selection of spectrum powers (And advanced spectrum powers starting at 12th level), which replace essentially Arcane Discoveries and range from Darkvision to a tar-like, slowing aura up to a multitude of improved mage-hands and the ability to spontaneously convert spells into associated energies.
The pdf also includes 4 different feats, two of which grant you access to additional spectrum and advanced spectrum powers, one that grants you access to another spectrum and one to suppress your mosaic aura.
Editing and formatting are not up to SGG's usual standard, there are more editing glitches in this pdf than usual. The pdf has no bookmarks and features neat artworks. layout adheres to SGG's 3-column standard.
The Mosaic Mages per se are an interesting concept in that their spell-selection is at once very wide and very limited - having access to both healing and arcane battle magic is interesting and might make the "Cleric/Druid-is-necessary" obsolete while still providing access to devastating battle-spells. On the other hand, the limitation to one energy-type (at least without taking feats/dual-spectrums) is a major drawback and I'm not entirely sold on the idea or the in-game balance of the different spectrum powers among the respective selections. The fact that the aura makes being a mosaic mage VERY obvious might make the class problematic for low-magic settings unless you make the color-aura only pop up when casting. The Mosaic Mages are not necessarily too versatile and the color-coding makes them a bit more predictable than I personally enjoy. While the Mosaic Mages do succeed in providing a distinct playing experience, their spectrum powers and overall potential fall a bit short of what they could have been. Combines with the editing glitches, my final verdict will thus be 3 stars.