An-Nahl 16:13

Signs in the Subjection of Night and Day, the Sun and the Moon, and in that which grows on Earth

Allah mentions the mighty signs and immense blessings to be found in His subjection of night and day, which follow one another; the sun and moon, which revolve; the stars, both fixed and moving through the skies, offering light by which people may find their way in the darkness. Each of (these heavenly bodies) travels in its own orbit, which Allah has ordained for it, and travels in the manner prescribed for it, without deviating in any way. All of them are under His subjugation, His control and His decree, as Allah says:

(Indeed, your Lord is Allah, Who created the heavens and the earth in Six Days, and then He rose (Istawa) over the Throne. He brings the night as a cover over the day, seeking it rapidly, and (He created) the sun, the moon, the stars (all) subjected to His command. Surely, His is the creation and commandment. Blessed is Allah, the Lord of all that exists!) (7:54) Thus Allah says;

(Surely, in this are proofs for people who understand.) meaning, they are indications of His immense power and might, for those who think about Allah and understand His signs.

(And whatsoever He has created of varying colors on the earth for you. ) When Allah points out the features of the skies, He also points out the wondrous things that He has created on earth, the variety of its animals, minerals, plants and inanimate features, all having different colors and shapes, benefits and qualities.

(Verily, in this is a sign for people who reflect.) meaning (those who remember) the blessings of Allah and give thanks to Him for them.

Then, in verse 13, after mentioning all other varied produce of the land, it was said: إِنَّ فِي ذَٰلِكَ لَآيَةً لِّقَوْمٍ يَذَّكَّرُ‌ونَ (Surely, in that, there is a sign for a people who accept advice). The sense is that no deep thinking is needed here as well - because, the proof has been furnished openly. But, the condition is that one must look at it carefully and learn his lesson. Otherwise, one who has no sense or concern and who just pays no attention could hardly hope to benefit from it.