In color theory, two colors are called complementary if, when mixed in the proper proportion, they produce a neutral color (grey, white, or black). Thus
Red and Green colors are complementary to each other
Therefore Mercury and Mars is enemies, as Red and Green cosmic rays can neutralize each other.
Same is the case With Blue and Orange; both colors are complementary to each other and can neutralize each other…
That is why Saturn and Sun are inimical to each other (but remember that they may also neutralize the bad effect of each other or may purify each other)
Similarly, Venus and Jupiter are enemy, as yellow and violet are complementary to each other and can neutralize each other's auspicious results.
Complementary colors when placed side by side make each other appear brighter.

So for example if Jupiter and Venus are placed in 2nd and 12th Houses from each other, they will become temporary friends and will start promoting each other.
Same is the case when Mars and Mercury are placed in 2nd and 12th Houses from each other.
For your information, Venus and Jupiter together can cause bloody battles on mundane level especially when they are in Trine to each other but this is only one of the many factors.

Now understand things more deeply that how exactly we can learn astrology through the colors of planets involved.
Consider the conjunction of Jupiter and Mars.
Jupiter has Yellow color cosmic rays, and Mars has Red color cosmic rays. Their perfect Yog will result into orange color of the Sun.
So the perfect Yog of Jupiter and Mars will give the effect of the Sun.

But here analysis would be different as the Sun is the Lord of only 1 Raashi that is Leo.

However when we talk of the Combined effect of Jupiter and Mars then we know that they together are the Lords of 4 Raashi's (Sagittarius, Pieces for Jupiter, and Aries and Scorpio for Mars). As a result, the effect of the combination of 2 planets is always greater than the effect of an individual planet which is the Sun in this case.

For your information, combined effect of the combination of Jupiter and Mars is 72 years (the highest possible in any Yog of in astrology); similarly that of Saturn and Venus Yog is 48 years as per the Lal Kitab. (you can refer Lal kitab for life term of other Yog)
So I have given you one clue to interpret the abrupt looking conclusions of Lal Kitab (Red Book).

Anyways similarly. perfect Yog of Jupiter and Saturn (Yellow and Blue colors) will fructify Green color, that resembles Mercury.
[Perfect means equal proportion of two colors]  So perfect Yog of Jupiter and Saturn will work like Mercury.

In fact more intense than actual Mercury, reason you know, Mercury lords over only 2 Raashi but Jupiter and Saturn when combined lord over 4 Raashi plus Jupiter also have 5th, and 9th full aspects to its credit and Saturn have 3rd and 10th full aspects in its lap apart from their 7th aspects which Mercury also have.

We can also understand the process and effect of planetary combinations through the color of their cosmic rays with the help of color wheel where two equilateral triangles inverse to each other can be placed on a circle.
One equilateral triangle is formed by primary colors - Red, Blue, and Yellow, and
second inverse equilateral triangle is formed secondary colors - Violet, Green and Orange.
In between the secondary and primary color we have the tertiary colors, for example, between blue and violet we have indigo (tertiary)
Just type color wheel on Google to know more about it.

Moving ahead, we must remember that we all are nothing but a unique combination of 7 colors of light, i.e. at the time when we were born on a specific time at a specific location, a particular unique combination of 7 colors of light was available in that environment.

Scientists may call it as a different set of electromagnetic radiation field on a specific time and location defined/modified by different levels of wavelength, frequency, intensity, absorption, reflection, emission, refraction with reference to light etc.

We astrologers are obviously are sitting on a much higher level of understanding when compared to the understanding derived from available scientific tools and can therefore take care of all the above mentioned aspects plus many additional hidden parameters which are not even known by science, through the concepts of astrology and are able to define levels of strengths of each cosmic ray by determining the strength of each planet. Not only this, but we are also able to time the effects of those planets through various Dashaa systems.
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VIBGYOR directly relate to 7 full Graha also to 7 Chakra of human energy system.
If we reverse and write
R - Mars - Moolaaadhaar - We say earth or grounding. Mars rules land
O - Moon - Swaadhishthaan - Mind/creativity. Seat of all desires
Y - Sun - Manipoor - Source of our all energy. Aptly called solar-plexus.
G - Mercury - Anaahat - abundance/healing. Feeling of silent love
B - Jupiter - Vishuddha - Expression/communication/purification. Shiv, retained the deadly poison Halaahal derived during Samudra Manthan, in his neck region.
I - Venus - Aagyaa - Intuition
V - Saturn - Sahasraar - Meditation/ultimate state of existence. No doubt, all extra-ordinary achievements need the support of Saturn.

Additionally, we have IR (Infra-red) and UV (ultra-violet) too.
By the above logic and formula that Raahu - Ketu are similar to Saturn and Mars (Shanivat Raahu and Kujaavat Ketu)
Ultra-Violet Rays - Raahu, and Infra-Red Rays- Ketu

Also there is special importance given to Violet. It is said that it increases one's mind powers, creativity etc. Leonardo da Vinci once wrote that meditation and prayer is ten times more powerful while sitting in the violet light.
But colors would always remain debatable, as each seer interprets it as different as per their own pre-concepts.