The Context Sentence for the vocabulary word 紅 (Deep Red) seems like it doesn’t work.
The reading that I’m being taught is くれない , but in the context sentence
it looks like it is the compound word where it’s just the on’yomi instead.
I did also report it via email, but wanted to see if I’m missing something.
While 紅色 can be read as こうしょく, I think the べにいろ reading is the most common, followed by くれないいろ, though I’m having trouble googling up the exact stats to prove it.
Colour words generally take the kun’yomi reading as the most common - compare 青色, 黄色, 灰色 et al.
Aye, but the trouble with that site is that it’s only considering the readings of words that have furigana included, so it may not be the most reliable guide. That’s most likely why it’s got くれない as the third reading rather than くれないいろ. Though considering it supports my own assertion, perhaps I shouldn’t be calling it into doubt. 
As a point of comparison, see the listing for 一. Or 効率.
Thanks for the replies! That was super helpful.
I forgot about all the other words which read as kun’yomi plus いろ . That makes more sense now.
And then it was reinforced with Google Translate’s reading of that context sentence.
Still might make sense to have a sentence that clearly uses the reading they are trying to reinforce.
In principle, learning resources like WK should just provide furigana on example sentences, especially where more than 1 reading is possible.
The most common out of cases where furigana was provided. They have a disclaimer
作品の中でふりがなが振られた語句のみ
What’s actually most common depends on how people read it in cases without furigana.
That said, wikipedia also lists べにいろ first and has a few words on the origins of all 3 readings.
Youtube sample size 紅色 | 15 pronunciations of 紅色 in Japanese is unfortunately very small and heavily influenced by 薄紅（うすべに）色 rather than 紅色 itself, so it’s difficult to draw conclusions from that one.