Doctrine of Colourable Legislation vs Colourable Exercise of Power

Imagine you're at a Delhi street food stall, and the vendor gives you a free dosa with chutney. You think, "Wow, what a great gesture!" But then, they say, "You see, there's a government scheme where we have to give free dosas to students between 12 pm and 1 pm." In this case, the vendor is trying to justify their gesture by citing a colourable legislation (a fake or non-existent government scheme). But if you ask them to show the government's notification, they'll say, "Oh, it's a colourable exercise of power, it's under the head 'Goodwill Gesture'." Here, the vendor is trying to cover up their own action by misusing administrative power.