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Black, Blue, Light blue. I have noticed different colored solar panels everywhere I go. I have a black solar panel that is installed on a solar flash light I also look on other people's houses to see a blue colored solar panels. Every time I ride the bus I see brand new houses with built in light blue solar panels. So why are solar panels different colors.

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Reasons for differing blue to black hues in very common silicon panels would be different manufacturing methods and how they reflect light a bit differently due to the material (crystal) arrangement.

Cut from pure drawn crystalline silicon bars, the cell material for monocrystalline panels can have a more uniform black color and broader light absorption at a particular angle.

Made from silicon offcuts, polycrystalline panels (also known as multicrystalline) are molded into rectangular block cells using several bits of crystal. This arrangement prevents perfect alignment and joints in the material causing more varied reflection at different angles and a generally more blue appearance.

(Though less efficient from a singular angle, there are applications that make the second type just as effective given various circumstances due to the varied-angle cell material.)

Hybrid constructions can create varied blue to black appearances. There are examples of less efficient cells that reflect yet other colors that are being developed to encourage adoption for broader construction and design purposes or applications.

Less common panels of other types and materials (including thin film types) will have their own material and manufacturing peculiarities. One example is a measurable darkening effect of the glass when ionized atoms of insulating material move creating fields giving rise to color fields. Special treatments or processes (like glass doping) can alleviate or modify these effects but can increase cost.

Unless a particular color is desirable, there are many different factors that determine precisely what color occurs in the final product. Along with market forces and required purpose, the final hue has more to do with the interplay of materials (layered substrate/conductor/window/absorber) decided on during the design and eventually replayed through an engineered manufacturing process.

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    Nice answer, but I'm not sure about the colored solar panels being less efficient. According to this article giving solar panels color doesn't affect their efficiency. However, the article contradicts itself by stating that not every color allows you to generate the same amount of electricity. I guess some colors don't affect efficiency and other do. – THelper Oct 11 '15 at 6:15
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    ... and not all panels are crystalline silicon: there's non-negligible quantities of CdTe, amorphous silicon and CI(G)S (pdf, see p20) – EnergyNumbers Oct 11 '15 at 16:39
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    I edited to include the efficiency reference that warranted my statement and tried to expand the answer to include and differentiate other materials and panel creation processes. – jmmygoggle Oct 13 '15 at 20:47

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