Why do CAs and accountants use green ink?
Green represents Budh (Mercury), and finance and accounts belong to Mercury. Using the colour of the planet that rules the work strengthens it; even clothes and pen ink act as interior vastu, which is also why lawyers choose black.
Related questions
If Mars as the 10th lord (karmesh) is debilitated, should red be avoided in the logo?
Yes. A debilitated karmesh does not support you, so avoid its colour in the business and the logo, and take the colour of the 11th lord (labhesh) instead.
Businesses and homes mostly use mixed colours. Should the zones still be followed?
Mixed colours are normal; a business uses several colours in its logo, flex, sign board, letterhead and visiting cards. Which colours to take from the kundali for business, study, spirituality and luck, and how to balance one's direction and element, is taught in the astro-vastu part.
How can I choose the colour that awakens my fortune for my bedroom if I have no horoscope or cannot read it?
Take a colour catalogue and turn its pages with your own eyes: the colours you are drawn to are the ones that awaken your fortune. Use that colour along with the colour of the zone you sleep in, and if possible match it with your horoscope; it usually matches. Sleeping steadily for eight hours in that colour lets its planet act on the whole body.
If the 10th lord is debilitated in the 4th house, which colour can be used?
Apply the neech bhang chain: see the sign where it is debilitated, the lord of that sign, and the sign where that lord is exalted. For example, Saturn debilitated in sign 1 leads to Mars, which is exalted in sign 10, ruled by Saturn again, so donate Saturn's items instead.
Is a dark grey background necessary, for example when making videos?
No, it is not necessary; many videos are made without any dark colour. If Saturn or Rahu is strong in your kundali, dark colours may even suit you. A video is short, so do not worry much about it; think carefully about colours in the office and bedroom, where you spend long hours.
My west-facing house has a lot of grey and it now feels irritating; what should I do?
With Saturn and Rahu in the 8th house in sign 8 (Rahu debilitated), grey should not have been used. Change the wall colour of the largest carpet area; the furniture need not change. Off-white walls are fine, so no need to worry about them.