Color of input placeholders too light/dark

[clemente-xyz]

Expected behavior

Users should recognise easily what the placeholders of the inputs say.

Actual behavior

Due to the color of them (too light on light-mode or too dark on dark-mode), is very hard to recognise what they say.

Steps to reproduce

One example to where to realise this issue is on the send token form:

1. Login to an account with balance.
2. Click on the "Send tokens" button of the Home tab.
3. Realise that the recipient address placeholder is very hidden and hard to read.

Which version(s) does this affect? (Environment, OS, etc...)

All.

[clemente-xyz]

Closing ticket since was already solved on previous changes.