“An optimist is a person who sees a green light everywhere, while the pessimist sees only the red spotlight... The truly wise person is colour-blind.”
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Albert Schweitzer 126
French-German physician, theologian, musician and philosoph… 1875–1965Related quotes

“A pessimist is a person who has had to listen to too many optimists.”

“The optimist sees the donut, the pessimist sees the hole.”

This quote is commonly attributed to Churchill, but appears in the "Red Herrings: False Attributions" appendix of Churchill by Himself : The Definitive Collection of Quotations (2008) by Richard Langworth, without citation as to where it originates.
In American Character, a 1905 address by Brander Matthews, a similar quotation is attributed to L. P. Jacks ( link http://hdl.handle.net/2027/mdp.39015059451156?urlappend=%3Bseq=238).
""Our civilization is a perilous adventure for an uncertain prize... Human society is not a constructed thing but a human organization... We are adopting a false method of reform when we begin by operations that weaken society, either morally or materially, by lower its vitality, by plunging it into gloom and despair about itself, by inducing the atmosphere of the sick-room, and then when its courage and resources are at a low ebb, expecting it to perform some mighty feat of self-reformation... Social despair or bitterness does not get us anywhere... Low spirits are an intellectual luxury. An optimist is one who sees an opportunity in every difficulty. A pessimist is one who sees a difficulty in every opportunity... The conquest of great difficulties is the glory of human nature." L. P. Jacks, quoted in American character, by Brander Matthews, 1906
Misattributed
Variant: A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty.

“A wise person is one who sees the effect of an action before he acts.”
Source: Fire without Fuel - The Aphorisms of Baba Hari Dass, 1986, p.41
“[…] You see, you are an optimist and live on hope. I am a pessimist and live on experience.”
Page 352-353.
Stepping Westward (1965)

His observations on the "strange events in our solar system" and as to why the sky looked blue and red colour was used in traffic lights to signal to vehicles to stop.
When Prof Jayant Narlikar saw the sun rise in the west

Source: 1830s, Nature http://www.emersoncentral.com/nature.htm (1836), Ch. 1, Nature
Context: The charming landscape which I saw this morning, is indubitably made up of some twenty or thirty farms. Miller owns this field, Locke that, and Manning the woodland beyond. But none of them owns the landscape. There is a property in the horizon which no man has but he whose eye can integrate all the parts, that is, the poet. This is the best part of these men's farms, yet to this their warranty-deeds give no title. To speak truly, few adult persons can see nature. Most persons do not see the sun. At least they have a very superficial seeing. The sun illuminates only the eye of the man, but shines into the eye and the heart of the child. The lover of nature is he whose inward and outward senses are still truly adjusted to each other; who has retained the spirit of infancy even into the era of manhood. His intercourse with heaven and earth, becomes part of his daily food.