So, the rate at which they grow does seem to always be the same, but by timing what I meant was when within the song itself I should tap. The sections with purples and 2 reds shows what I had originally assumed well
🟣>wait 1 beat>🟣>wait 1 beat>🔴>wait half beat>🔴>wait half beat>🟣>wait 1 beat>🟣>wait 1 beat
So I assumed that purples told me to wait a full beat, and red told me to wait half a beat. But when the pattern changes to give you all reds, the interval between them is 1 beat again, this is what got me confused.
On the other hand, it is clear that each color does take a fixed time to go from spawning to blinking white, such as the greens being the really quick ones. It's just that I thought the colors were informing me of the timing of the music, and not of the circles themselves.
edit: I did mention Osu, but I'm much more of a pump it up player myself, so I'm less used to the notes telling you anything other than their timing (and which button to press, in pump it up's case)