Red investors oceans represent to all the industries in existence today – the known Investor space. In the red oceans, investors boundaries are defined and accepted, and the competitive rules of the game are known. Here start-ups try to outperform their other start-ups rivals to grab a greater share of investment demand. As the funding market space gets crowded, prospects for high valuation and rapid investments are reduced. Products become commodities or niche, and cutthroat competition turns the ocean bloody; hence, the term red oceans.
Blue investor oceans, in contrast, denote all the industries not in existence today – the unknown investor market space, untainted by start-up competition. In blue oceans, investment demand is created rather than fought over. There is ample opportunity for high valuation and rapid investment. In blue oceans, start-up competition for funding is irrelevant because the rules of the game are waiting to be set. Blue investment ocean is an analogy to describe the wider, deeper potential of investor space that is not yet explored.
(Adaptation of Wkipedia article on blue ocean strategy for investment for start-ups)
In your article the "guilder-investing angels" are the blue ocean for investment in start-ups.