Don't know if it should be read as まいろ, まあいろ, あさいろ or in some other way. Couldn't find it in any dictionary.
Context: 
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Out of interest, what game is that? (I'm fond of old games.) – oals Apr 13 '15 at 19:31
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1It's 雫 by Leaf, original PC-98 edition. – mio Apr 13 '15 at 19:36
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It's just a trivia but 雫 was written by 高橋龍也 in 1996. His latest work in 2015 is アイドルマスター シンデレラガールズ. – marasai Apr 14 '15 at 11:48
It's read like a regular compound word, あさいろ
Here's a passage from Aozora Bunko with furigana:
何か妙な[粉]{こな}をふりかけた[麻色]{あさいろ}の[縮]{ちぢ}れ毛の[鬘]{かずら}である。
灰 (はい)
灰色 (はいいろ)
茶 (ちゃ)
茶色 (ちゃいろ)
黄 (き)
黄色 (きいろ)
銀 (ぎん)
銀色 (ぎんいろ)
I'm not 100% sure, but the trend seems to be attaching いろ directly to the standalone word. Going from this, I would assume that 麻色 is read as あさいろ.
Apologies for not being able to provide a confident answer.
